Amorphous silicon-thick film lithium niobate hybrid integrated bend converter and method of making same

Abstract

The application belongs to the technical field of integrated optical devices, and discloses an amorphous silicon-thick film lithium niobate hybrid integrated bending converter and a preparation method thereof. The thick film lithium niobate layer of the device is photoetched to form a thick film lithium niobate end face coupler, a first thick film lithium niobate waveguide and a second thick film lithium niobate waveguide. The amorphous silicon layer comprises a first and a second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure and an amorphous silicon bending waveguide. The optical signal transmitted in the first thick film lithium niobate waveguide can be transmitted to the amorphous silicon bending waveguide and finally transmitted to the second thick film lithium niobate waveguide, so that the bending conversion output is realized. The amorphous silicon functional component is introduced between the two thick film lithium niobate waveguides, so that the problems of weak optical binding capacity of the thick film lithium niobate bending waveguide and large bending radius of the waveguide are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of integrated optical device technology, and more specifically, relates to an amorphous silicon-thick-film lithium niobate hybrid integrated bending converter and its preparation method. Background Technology

[0002] Lithium niobate (LiNbO3, LN) is a negative uniaxial crystal with non-centrosymmetry and a wide wavelength transmission range, approximately 350 nm to 5500 nm. This crystal exhibits excellent physical properties, encompassing superior piezoelectric, dielectric, ferroelectric, electro-optic, acousto-optic, and nonlinear optical properties. Therefore, it is considered the best-performing ferroelectric material in terms of overall performance and is known as "optical silicon" due to its outstanding optical properties. Traditional lithium niobate materials have already been widely used in modulators, fiber optic gyroscopes, and fiber optic sensors, demonstrating their mature development and excellent performance characteristics.

[0003] With technological advancements, lithium niobate thin films prepared using ion cutting technology have gradually entered the market. However, due to their relatively thin thickness (typically below 1 μm and above 200 nm), thin-film lithium niobate results in ridge waveguide mode field sizes smaller than 1 μm, while optical fiber mode fields are typically greater than or equal to 3 μm, leading to a size mismatch. This mismatch can significantly increase coupling loss between the fiber and the waveguide. Furthermore, thin-film lithium niobate performs weaker in high-power applications compared to thick-film lithium niobate (typically exceeding 1 μm in thickness). Thick-film lithium niobate, due to its greater thickness, has relatively weaker lateral mode field confinement, making it prone to mode field leakage in bent waveguides, thus increasing losses. For example, a thick-film lithium niobate film with a thickness of 3 μm to 5 μm requires a bent waveguide radius of over 1 mm, exhibiting weak lateral optical confinement and a large waveguide bending radius. The thicker the lithium niobate film, the weaker the lateral confinement, and the larger the required radius. These characteristics need to be comprehensively considered and optimized for specific applications. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide an amorphous silicon-thick-film lithium niobate hybrid integrated bending transducer and its fabrication method. This transducer introduces an amorphous silicon functional component (including a first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, an amorphous silicon bending waveguide, and a second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure; amorphous silicon straight waveguides can be optionally provided before and after the amorphous silicon bending waveguide) between two thick-film lithium niobate waveguides. Due to the high refractive index of amorphous silicon and its ability to form a high refractive index difference with lithium niobate, the problems of weak optical confinement and large waveguide bending radius in thick-film lithium niobate bending waveguides are effectively solved. Furthermore, the device of this invention can conveniently achieve low-loss bending transmission of optical signals and can simultaneously perform filtering. It is simple to fabricate and can effectively improve device performance and fabrication efficiency.

[0005] To achieve the above objectives, according to one aspect of the present invention, an amorphous silicon-thick-film lithium niobate hybrid integrated bending converter is provided, characterized in that it comprises, from bottom to top: a substrate layer (1), a buried oxide layer (2), a thick-film lithium niobate layer (3), an amorphous silicon layer (5), and a dielectric film material layer (6) with a refractive index less than 2, wherein,

[0006] The thick-film lithium niobate layer (3) is photolithographically etched to form a thick-film lithium niobate end-face coupler (7), a first thick-film lithium niobate waveguide, and a second thick-film lithium niobate waveguide. The thick-film lithium niobate end-face coupler (7) is connected to the input end of the first thick-film lithium niobate waveguide. The waveguide directions of the first thick-film lithium niobate waveguide and the second thick-film lithium niobate waveguide are not parallel to each other and are at a predetermined angle to each other.

[0007] The amorphous silicon layer (5) has a first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, an amorphous silicon curved waveguide (9), and a second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure connected in sequence. The first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is connected to the output end of the first thick-film lithium niobate waveguide, and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is connected to the input end of the second thick-film lithium niobate waveguide. In this way, the optical signal transmitted in the first thick-film lithium niobate waveguide can be transmitted to the amorphous silicon curved waveguide (9) through the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, and finally transmitted to the second thick-film lithium niobate waveguide through the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, thereby realizing curved conversion output.

[0008] The overall thickness of the thick-film lithium niobate layer (3) is greater than 1 μm.

[0009] As a further preferred embodiment of the present invention, the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is connected to the amorphous silicon bent waveguide (9) via an amorphous silicon straight waveguide (10).

[0010] Alternatively, the amorphous silicon curved waveguide (9) and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure can be connected by an amorphous silicon straight waveguide (10).

[0011] As a further preferred embodiment of the present invention, the output end of the first thick-film lithium niobate waveguide is perpendicularly evanescently coupled to the input end of the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure.

[0012] The output end of the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is perpendicularly evanescently coupled to the input end of the second thick-film lithium niobate waveguide;

[0013] The first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure both have an isosceles trapezoidal shape projected onto the surface of the substrate layer (1).

[0014] Preferably, the widths of the thick-film lithium niobate end coupler (7), the first thick-film lithium niobate waveguide, and the second thick-film lithium niobate waveguide are all equal, all being w0. The length of the upper base of the isosceles trapezoid is w1, and the length of the lower base of the isosceles trapezoid is w2. When w0 is 3 μm, w1 is 0.12 μm, and w2 is 0.45 μm, for any isosceles trapezoid, the height l of the isosceles trapezoid is greater than or equal to 800 micrometers.

[0015] As a further preferred embodiment of the present invention, the amorphous silicon bent waveguide (9) is arc-shaped with a radius of 5μm to 300μm;

[0016] Alternatively, the amorphous silicon bent waveguide (9) is an Euler bent waveguide with an equivalent radius R. eff The range is from 5μm to 300μm.

[0017] As a further preferred embodiment of the present invention, the amorphous silicon bent waveguide (9) is an Euler bent waveguide; in this case, the amorphous silicon-thick film lithium niobate hybrid integrated bent converter also has a filtering function.

[0018] As a further preferred embodiment of the present invention, the overall thickness of the thick film lithium niobate layer (3) is greater than 1 μm and less than or equal to 10 μm.

[0019] As a further preferred embodiment of the present invention, the thickness of the amorphous silicon layer (5) is 200-340 nm.

[0020] As a further preferred embodiment of the present invention, the substrate layer (1) is specifically a silicon substrate layer, a quartz substrate layer or a sapphire substrate layer;

[0021] The dielectric film material layer (6) with a refractive index less than 2 is made of at least one of silicon dioxide, aluminum oxide, silicon oxynitride, SU8 photoresist, and SOG spin-coated glass.

[0022] According to another aspect of the present invention, the present invention provides a method for fabricating the above-mentioned amorphous silicon-thick-film lithium niobate hybrid integrated bending converter, characterized by comprising the following steps:

[0023] S1. Prepare a silicon-based thick-film lithium niobate material substrate, wherein the silicon-based thick-film lithium niobate material substrate comprises, from bottom to top, a substrate layer, a buried oxide layer and a thick-film lithium niobate layer, wherein the thickness of the thick-film lithium niobate layer is greater than 1 μm; a thick-film lithium niobate optical structure is fabricated on the thick-film lithium niobate layer of the silicon-based thick-film lithium niobate material substrate using photolithography etching technology to form a thick-film lithium niobate end-face coupler (7), a first thick-film lithium niobate waveguide and a second thick-film lithium niobate waveguide;

[0024] S2. Amorphous silicon is grown on the substrate obtained in S1 using thin film deposition, and the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, the amorphous silicon bent waveguide (9), and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure are sequentially connected by photolithography etching technology.

[0025] S3. By covering the substrate obtained in S2 with a dielectric film material with a refractive index less than 2 through thin film deposition or spin coating, an amorphous silicon-thick film lithium niobate hybrid integrated bending converter can be obtained.

[0026] As a further preferred embodiment of the present invention, in step S2, the amorphous silicon straight waveguide (10) is also prepared by the photolithography etching technique;

[0027] In step S1, the photolithography etching technology is based on stepper lithography machine, contact lithography machine, projection lithography machine, electron beam direct writing or laser direct writing;

[0028] In step S2, the thin film deposition method is specifically at least one of physical vapor deposition and chemical vapor deposition; the photolithography etching technology is based on stepper lithography machine, contact lithography machine, projection lithography machine, electron beam direct writing or laser direct writing;

[0029] In step S3, the thin film deposition method is specifically at least one of physical vapor deposition and chemical vapor deposition.

[0030] Compared with existing technologies, the technical solution conceived in this invention, by introducing an amorphous silicon functional component (including a first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, an amorphous silicon bent waveguide, and a second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure; an amorphous silicon straight waveguide can be optionally set before and after the amorphous silicon bent waveguide) between two thick-film lithium niobate waveguides, effectively solves the problems of weak optical confinement capability and large waveguide bending radius in thick-film lithium niobate bent waveguides, and can conveniently realize low-loss bent transmission of optical signals. Taking laser transmission as an example, after the laser is coupled to the waveguide through the thick-film lithium niobate end-face coupler, it is coupled to the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure to achieve bent optical transmission. After bent transmission is completed, it is coupled back to the thick-film lithium niobate waveguide through the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure for subsequent functional implementation.

[0031] Specifically, the present invention can achieve the following beneficial effects:

[0032] 1. This invention utilizes the advantages of amorphous silicon, such as its high refractive index and ability to form a high refractive index difference with lithium niobate, to combine it with thick-film lithium niobate, thus solving the problem of weak optical confinement capability in thick-film lithium niobate curved waveguides. As illustrated in the embodiments below, due to the introduction of the amorphous silicon functional component, the bending radius of the device of this invention can be as small as 5μm (for arc-shaped curved waveguides) and 5μm (for Euler curved waveguides), and the loss is low (as illustrated in the embodiments below, when R...). eff With a wavelength of 14.5 μm, the device loss in TE0 mode at a wavelength of 1.55 μm is only 0.035 dB, which is significantly smaller than the radius of a thick-film lithium niobate bent waveguide.

[0033] 2. The amorphous silicon-thick-film lithium niobate hybrid integrated bending converter of this invention can continue to leverage the advantages of thick-film lithium niobate, such as its strong thermal stability and ability to withstand high-power lasers. The introduction of amorphous silicon bending waveguides lays the foundation for the integration of thick-film lithium niobate. The bending converter obtained by this invention provides possibilities for thick-film lithium niobate integration platforms and lays the foundation for the development of high-power integrated devices. Thick-film lithium niobate material has high thermal conductivity, meaning it can transfer heat more effectively. As power increases, the material can dissipate heat from the heat source more quickly, thereby maintaining a relatively stable temperature, reducing heat accumulation, and facilitating long-term high-power operation. The introduction of amorphous silicon bending waveguides in this invention allows for the use of smaller bending radii, reducing the device footprint on the thick-film lithium niobate platform, improving integration density, and facilitating the packaging of thick-film lithium niobate devices. Traditional diffused waveguides or ridge waveguide structures etched from lithium niobate bulk materials often employ 90-degree bends in their radio frequency electrodes. The amorphous silicon-thick-film lithium niobate hybrid integrated bending converter in this invention provides more options for the light incident / emission ports, enabling 90-degree bends and improving packaging flexibility.

[0034] 3. The amorphous silicon-thick film lithium niobate hybrid integrated bending converter of the present invention, wherein the amorphous silicon bending waveguide is preferably an Euler bending waveguide, so that the amorphous silicon-thick film lithium niobate hybrid integrated bending converter, in addition to having the function of bending transmission, can also support only TE0 and TM0 modes, and has the function of filtering out other higher-order modes (i.e., has a filtering effect), achieving the function of filtering modes while realizing compact turning, thereby selecting the mode required by the integrated device.

[0035] 4. The process steps adopted are low-cost and the manufacturing process is simple, and it is well compatible with CMOS technology. Attached Figure Description

[0036] Figure 1 This is a top view of the overall device of the amorphous silicon-thick film lithium niobate hybrid integrated bending converter in this invention.

[0037] Figure 2 The diagram shows the cross-sectional structure of the amorphous silicon-thick film lithium niobate hybrid integrated bending converter at different dashed lines in this invention.

[0038] Figure 3 This is a graph showing the relationship between the width w0 of the thick-film lithium niobate end-face coupler and the transmission loss in this invention.

[0039] Figure 4 This is a top view of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure in this invention (the inset in the figure shows the TEO mode optical mode field diagram at the location indicated by the dashed line).

[0040] Figure 5The diagram shows the relationship between the length l of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure and the transmission loss in this invention (at this time, w0 is 3 μm, w1 is 0.12 μm, w2 is 0.45 μm, and the thickness of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is 0.22 μm).

[0041] Figure 6 This is a graph showing the relationship between the effective refractive index of the amorphous silicon waveguide mode and the width w2 in this invention.

[0042] Figure 7 The diagram shows the transmission loss relationship between the intrinsic modes of the amorphous silicon bent waveguide in this invention and the wavelength (the inset in the figure is the optical mode field diagram at a wavelength of 1.55 μm).

[0043] Figure 8 This is a flowchart illustrating the fabrication method of the amorphous silicon-thick-film lithium niobate hybrid integrated bending converter device in this invention.

[0044] Figure 9 This is a graph showing the transmission loss relationship of the intrinsic modes of the amorphous silicon curved waveguide with a radius of 5 μm as a function of wavelength in Embodiment 2 of the present invention (the inset in the figure is the optical mode field diagram at a wavelength of 1.55 μm).

[0045] Figure 10 The diagram shows the transmission loss relationship of the intrinsic modes of the amorphous silicon bent waveguide in Embodiment 2 of the present invention as a function of wavelength (the inset in the figure is the optical mode field diagram at a wavelength of 1.55 μm).

[0046] Figure 11 This diagram compares the traditional 90-degree corner packaging method for RF electrodes with the 90-degree corner packaging method for incident / emission optical coupling ports. Figure 11 (a) in the text corresponds to the traditional 90-degree corner packaging method for RF electrodes. Figure 11 (b) in the figure represents the 90-degree corner packaging method for the incident / outgoing optical coupling port (applicable to this invention).

[0047] Figure 1 , Figure 2 and Figure 4 In the figures, the meanings of the reference numerals are as follows: 1-substrate layer (e.g., silicon substrate), 2-buried oxide layer, 3-thick film lithium niobate layer, 4-thick film lithium niobate waveguide, 5-amorphous silicon layer, 6-dielectric film material with refractive index less than 2 (i.e., dielectric film material layer with refractive index less than 2), 7-thick film lithium niobate end coupler, 8-amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, 9-amorphous silicon bent waveguide, 10-amorphous silicon waveguide (i.e., amorphous silicon straight waveguide). Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Example 1

[0050] like Figure 1 and Figure 2 As shown, an amorphous silicon-thick-film lithium niobate hybrid integrated bend transducer includes a thick-film lithium niobate end-face coupler 7, a thick-film lithium niobate waveguide 4, an amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8, an amorphous silicon bend waveguide 9, and an amorphous silicon waveguide 10. There are two thick-film lithium niobate waveguides 4 (a first thick-film lithium niobate waveguide and a second thick-film lithium niobate waveguide), and two amorphous silicon-lithium niobate wedge waveguide optical mode conversion structures 8 (a first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure and a second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure); as... Figure 1 As shown, the thick-film lithium niobate end-face coupler 7 is connected to the thick-film lithium niobate waveguide 4. The output end of the thick-film lithium niobate waveguide 4 is connected to the amorphous silicon bent waveguide 9 through the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8. The output end of the amorphous silicon bent waveguide 9 is connected to the amorphous silicon waveguide 10. The output end of the amorphous silicon waveguide 10 is then connected to the thick-film lithium niobate waveguide 4 through the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8. Furthermore, as shown, the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8, the amorphous silicon bent waveguide 9, the amorphous silicon waveguide 10, and the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8 at the other end are tightly connected. And, as... Figure 2 As shown, the device of the present invention comprises, from bottom to top, a silicon substrate layer 1 (in this embodiment, the thickness of this layer is 500 μm), a buried oxide layer 2 (in this embodiment, the thickness of this layer is 3 μm), a thick film lithium niobate layer 3 (in this embodiment, the overall thickness of this layer is 3 μm, and the thickness of the thick film lithium niobate waveguide 4 formed after etching is 2 μm), an amorphous silicon layer 5 (in this embodiment, the thickness of this layer is 0.22 μm), and a dielectric film material 6 with a refractive index less than 2 (in this embodiment, the thickness of this layer is 4 μm, specifically silicon dioxide material).

[0051] The thick-film lithium niobate end-face coupler 7 is connected to the thick-film lithium niobate waveguide 4. Its output end is connected to the amorphous silicon bent waveguide 9 through the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8. The output end of the amorphous silicon bent waveguide 9 is connected to the amorphous silicon waveguide 10, and is connected to the thick-film lithium niobate waveguide 4 through the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8.

[0052] In this embodiment, the width of the thick-film lithium niobate end-face coupler is the same as the width of the thick-film lithium niobate waveguide, and w0 is 3μm. Figure 3 The graph shows the relationship between the width w0 of the thick-film lithium niobate end-face coupler and the transmission loss. It can be seen that when w0 is 2.5μm to 3.5μm, the coupling loss between TE0 and TM0 of the thick-film lithium niobate end-face coupler is low and it has a large process tolerance.

[0053] In this embodiment, Figure 4 The diagram shows a top view of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure and the corresponding optical mode field diagram. It illustrates the optical mode pattern of light coupling from the thick lithium niobate layer to the amorphous silicon layer, showcasing its progression. After light is coupled from the thick lithium niobate end-face coupler 7 into the thick lithium niobate waveguide 4, it undergoes adiabatic coupling via the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8 using the evanescent wave coupling principle, thus transmitting the light to the amorphous silicon layer 5 for further propagation. The thick lithium niobate layer shown in the diagram has a width w0 of 3 μm, a thickness of 3 μm, and a 2 μm etched layer forming the thick lithium niobate waveguide 4 with a tilt angle of 65 degrees (the other end of the thick lithium niobate waveguide 4, connected to the thick lithium niobate end-face coupler 7, has the same width and thickness). The tip w1 of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is 0.12 μm, the width w2 of the amorphous silicon waveguide is 0.45 μm, and the length l of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is 900 μm (e.g., Figure 4 As shown, the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8 is a linear conical structure. That is, the projection shape of the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8 in the top view is an isosceles trapezoid, and the length l is the height of the isosceles trapezoid. The amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8, which is connected to the amorphous silicon bent waveguide 9 at the other end, also has the same values ​​for w1, w2, and l. The width of the amorphous silicon bent waveguide 9 is also 0.45 μm, and the thickness is 0.22 μm. Figure 5 To establish the relationship between length l and transmission loss (l can preferably be greater than or equal to 800 micrometers), low-loss transmission from the thick-film lithium niobate waveguide 4 to the amorphous silicon layer 5 is achieved.

[0054] Furthermore, light is coupled into the waveguide through the thick-film lithium niobate end coupler 7, and different modes exist. The corresponding intrinsic modes are obtained by filtering through the amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8 and the amorphous silicon bent waveguide 9.

[0055] The amorphous silicon bent waveguide 9 used is an Euler bend, and according to existing technology, its curvature is... L is the length of the curve from the starting point (0,0) to the position (x,y), R is the radius of curvature, and A is a constant. The constant A is expressed as... Where L0 corresponds to the endpoint position (x) e ,y e The length of the curve, where R = R min In Cartesian coordinates, it is represented as Through structural design, the waveguide supports only TE0 and TM0 modes, serving both filtering and eigenmode preservation functions. The amorphous silicon bent waveguide has a width of 0.45 μm and a thickness of 0.22 μm. max 30μm, R min 10μm (R) eff (approximately 14.5 μm).

[0056] Figure 6 The graph shows the relationship between the effective refractive index of the amorphous silicon waveguide mode and the width w2. It can be seen that only the TE0 and TM0 modes exist in the waveguide mode, which have a filtering effect.

[0057] Figure 7 The optical field diagrams of TE0 and TM0 modes in an amorphous silicon bent waveguide, along with the corresponding transmission losses for both modes, are shown. It is evident from the insets that at a wavelength of 1.55 μm, the modes remain unchanged, maintaining TE0 and TM0 transmission. Specifically, the TE0 mode maintains low-loss transmission at wavelengths of 1.5 μm–1.6 μm, while the TM0 mode exhibits higher loss compared to the TE0 mode. Therefore, the device of this invention is particularly suitable for application in TE0 mode, maintaining low-loss transmission.

[0058] In addition, such as Figure 8 As shown, the fabrication method of the above-mentioned amorphous silicon-thick film lithium niobate hybrid integrated bending converter includes the following steps:

[0059] S1. A thick-film lithium niobate optical structure is fabricated on a silicon-based thick-film lithium niobate material using photolithography etching technology. The structure includes a thick-film lithium niobate end-face coupler 7 and a thick-film lithium niobate waveguide 4 (that is, the thick-film lithium niobate end-face coupler 7 and the thick-film lithium niobate waveguide 4 are both formed by etching the thick-film lithium niobate layer 3; the etching depth is the thickness of the formed thick-film lithium niobate waveguide 4).

[0060] S2. Amorphous silicon is grown on the substrate obtained in step S1 using inductively coupled plasma chemical vapor deposition (ICPCVD), and amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure 8, amorphous silicon bent waveguide 9, and amorphous silicon waveguide 10 are fabricated using photolithography etching technology.

[0061] S3. On the substrate obtained in step S2, a dielectric film material with a refractive index less than 2 is deposited or spin-coated to obtain an amorphous silicon-thick film lithium niobate hybrid integrated bending converter.

[0062] The photolithography methods include: stepper lithography, contact lithography, projection lithography, electron beam direct writing, and laser direct writing; in this embodiment, a contact lithography machine is used. The thin film deposition methods include: physical vapor deposition and chemical vapor deposition; in this embodiment, chemical vapor deposition is used.

[0063] Example 2

[0064] This embodiment is based on Embodiment 1, only adjusting the amorphous silicon bent waveguide 9. The amorphous silicon bent waveguide 9 is respectively replaced by a circular arc-shaped bent waveguide with a radius of 5μm and an Euler bent waveguide with an equivalent radius of 5μm (R... max =7μm, R min =4μm) replacement, the bending waveguide width is 0.45μm.

[0065] Figure 9 and Figure 10 The transmission loss relationships of the eigenmodes as a function of wavelength are shown for a 5μm radius circular curved waveguide and an equivalent 5μm radius Euler curved waveguide, respectively. The inset in the figures shows the optical mode field at a wavelength of 1.55μm. (From...) Figure 9 and Figure 10 As can be seen from the figure, the TE0 mode transmits with low loss, and the mode does not change significantly. Compared to the TE0 mode, the TM0 mode has higher loss, and the TM0 mode changes during transmission. Therefore, the device of this invention is particularly suitable for use in TE0 mode, maintaining low-loss transmission. Furthermore, the figure also shows that it can operate normally with a bending radius (equivalent radius) of 5μm. A smaller bending radius (equivalent radius) can further reduce the device footprint, improve integration density, and reduce fabrication costs.

[0066] Example 3

[0067] Figure 11Two packaging methods are demonstrated: a traditional 90-degree corner packaging method for RF electrodes and a 90-degree corner packaging method for the incident / emission optical coupling port. By employing the amorphous silicon-thick-film lithium niobate hybrid integrated bending converter of this invention, the optical incident / emission port has more selectable directions, enabling a 90-degree corner and improving packaging flexibility. Furthermore, this invention can achieve not only 90-degree bending but also 180-degree bending, which is of great significance for realizing folded lithium niobate modulators on a thick-film platform.

[0068] The above embodiments are merely examples. For instance, the amorphous silicon waveguide 10 is an optional component; it can be omitted or flexibly placed before or after the amorphous silicon bent waveguide 9. Figure 1 Taking the amorphous silicon waveguide 10 positioned behind the amorphous silicon bent waveguide 9 as an example; of course, it can also be positioned both before and after the amorphous silicon bent waveguide 9. Furthermore, w0, w1, w2, and l can be flexibly adjusted according to actual needs (for example, the width w2 of the amorphous silicon straight waveguide is often a common width in the industry; w1 can often be the minimum width achievable by the process, and the smaller the value, the better (for example, it can be 180nm, 90nm, etc.); l can also be flexibly adjusted according to actual needs, as long as the loss meets the requirements). In addition, the amorphous silicon bent waveguide 9 can be an arc shape, an Euler bend waveguide, or other structures such as a cyclotron bend, a sine bend, a cosine bend, or a topology-optimized curve. According to existing processes, when the amorphous silicon bent waveguide 9 is arc-shaped, the radius from 5μm to 300μm is compatible with existing processes (of course, the specific radius can be flexibly adjusted); when the amorphous silicon bent waveguide 9 is an Euler bent waveguide, the equivalent radius R eff The waveguide diameter can range from 5μm to 300μm and is compatible with existing processes (of course, the specific radius can also be flexibly adjusted). In addition, the waveguide directions of the two thick-film lithium niobate waveguides are at a predetermined angle to each other, which can be any angle greater than 0 degrees and less than 180 degrees.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating an amorphous silicon-thick-film lithium niobate hybrid integrated bending converter, wherein the amorphous silicon-thick-film lithium niobate hybrid integrated bending converter comprises, from bottom to top: The structure consists of a substrate layer (1), a buried oxide layer (2), a thick lithium niobate layer (3), an amorphous silicon layer (5), and a dielectric film material layer with a refractive index less than 2 (6), wherein... The thick-film lithium niobate layer (3) is photolithographically etched to form a thick-film lithium niobate end-face coupler (7), a first thick-film lithium niobate waveguide, and a second thick-film lithium niobate waveguide. The thick-film lithium niobate end-face coupler (7) is connected to the input end of the first thick-film lithium niobate waveguide. The waveguide directions of the first thick-film lithium niobate waveguide and the second thick-film lithium niobate waveguide are not parallel to each other and are at a predetermined angle to each other. The amorphous silicon layer (5) has a first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, an amorphous silicon curved waveguide (9), and a second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure connected in sequence. The first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is connected to the output end of the first thick-film lithium niobate waveguide, and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is connected to the input end of the second thick-film lithium niobate waveguide. In this way, the optical signal transmitted in the first thick-film lithium niobate waveguide can be transmitted to the amorphous silicon curved waveguide (9) through the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, and finally transmitted to the second thick-film lithium niobate waveguide through the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, thereby realizing curved conversion output. The overall thickness of the thick-film lithium niobate layer (3) is greater than 1 μm; The preparation method is characterized by the following steps: S1. Prepare a silicon-based thick-film lithium niobate material substrate, wherein the silicon-based thick-film lithium niobate material substrate comprises, from bottom to top, a substrate layer, a buried oxide layer and a thick-film lithium niobate layer, wherein the thickness of the thick-film lithium niobate layer is greater than 1 μm; a thick-film lithium niobate optical structure is fabricated on the thick-film lithium niobate layer of the silicon-based thick-film lithium niobate material substrate using photolithography etching technology to form a thick-film lithium niobate end-face coupler (7), a first thick-film lithium niobate waveguide and a second thick-film lithium niobate waveguide; S2. Amorphous silicon is grown on the substrate obtained in S1 using thin film deposition, and the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure, the amorphous silicon bent waveguide (9), and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure are sequentially connected by photolithography etching technology. S3. By covering the substrate obtained in S2 with a dielectric film material with a refractive index less than 2 through thin film deposition or spin coating, an amorphous silicon-thick film lithium niobate hybrid integrated bending converter can be obtained.

2. The preparation method according to claim 1, characterized in that, In step S2, the photolithography etching technique also produces an amorphous silicon straight waveguide (10). In step S1, the photolithography etching technology is based on stepper lithography machine, contact lithography machine, projection lithography machine, electron beam direct writing or laser direct writing; In step S2, the thin film deposition method is specifically at least one of physical vapor deposition and chemical vapor deposition; the photolithography etching technology is based on stepper lithography machine, contact lithography machine, projection lithography machine, electron beam direct writing or laser direct writing; In step S3, the thin film deposition method is specifically at least one of physical vapor deposition and chemical vapor deposition.

3. The preparation method according to claim 1, characterized in that, The first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is connected to the amorphous silicon bent waveguide (9) via an amorphous silicon straight waveguide (10). Alternatively, the amorphous silicon curved waveguide (9) and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure are connected by an amorphous silicon straight waveguide (10).

4. The preparation method according to claim 1, characterized in that, The output end of the first thick-film lithium niobate waveguide is perpendicularly evanescently coupled to the input end of the first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure. The output end of the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure is perpendicularly evanescently coupled to the input end of the second thick-film lithium niobate waveguide; The first amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure and the second amorphous silicon-lithium niobate wedge waveguide optical mode conversion structure both have an isosceles trapezoidal projection shape on the surface of the substrate layer (1).

5. The preparation method according to claim 4, characterized in that, The thickness of the lithium niobate end coupler (7), the first thick-film lithium niobate waveguide, and the second thick-film lithium niobate waveguide are all equal in width, w0. The length of the upper base of the isosceles trapezoid is w1, and the length of the lower base is w2. When w0 is 3μm, w1 is 0.12μm, and w2 is 0.45μm, for any isosceles trapezoid, the height of the isosceles trapezoid is... l Greater than or equal to 800 micrometers.

6. The preparation method according to claim 1, characterized in that, The amorphous silicon bent waveguide (9) is arc-shaped with a radius of 5μm~300μm; Alternatively, the amorphous silicon bent waveguide (9) is an Euler bent waveguide with an equivalent radius R. eff The range is from 5μm to 300μm.

7. The preparation method according to claim 1, characterized in that, The amorphous silicon bent waveguide (9) is an Euler bent waveguide; at this time, the amorphous silicon-thick film lithium niobate hybrid integrated bent converter also has a filtering function.

8. The preparation method according to claim 1, characterized in that, The overall thickness of the thick lithium niobate layer (3) is greater than 1 μm and less than or equal to 10 μm.

9. The preparation method according to claim 1, characterized in that, The thickness of the amorphous silicon layer (5) is 200-340 nm.

10. The preparation method according to claim 1, characterized in that, The substrate layer (1) is specifically a silicon substrate layer, a quartz substrate layer or a sapphire substrate layer; The dielectric film material layer (6) with a refractive index less than 2 is made of at least one of silicon dioxide, aluminum oxide, silicon oxynitride, SU8 photoresist, and SOG spin-coated glass.

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