Electro-optic material thin film substrate, electro-optic modulating device and preparation method

Abstract

The application provides an electro-optical material film substrate, an electro-optical modulation device and a preparation method, and belongs to the technical field of optical phase modulators. The electro-optical material film substrate comprises a first substrate, a second bonding layer and a first bonding layer, the first bonding layer is provided with at least one group of parallel inverted V-shaped protrusions; an electro-optical material layer is located on the upside of the first bonding layer and comprises an electro-optical material layer slope and an electro-optical material layer mesa. The electro-optical modulation device comprises a second substrate, a lower cladding layer, a waveguide core, a third bonding layer, an electro-optical material film piece, electrodes and the like. The electro-optical material film piece comprises at least one electro-optical material layer mesa and a pair of electro-optical material layer slopes, the electro-optical material layer is bonded to the third bonding layer, the electro-optical material layer slopes and the waveguide core are overlapped in projection on the second substrate, the electrodes are located on the upside of the second bonding layer and on both sides of the waveguide core, and the partial length of the electrodes is located in the length range of the overlapping part of the waveguide core and the electro-optical material layer mesa in projection on the second substrate. The scheme reduces the optical field transition loss and has low process difficulty.

Description

Technical Field

[0001] This application relates to the field of optical phase modulator technology, and in particular to an electro-optic material thin film substrate, an electro-optic modulator device, and a preparation method thereof. Background Technology

[0002] In fields such as optical communication, optical computing, and optical sensing, phase modulation is fundamental for realizing complex optical signal processing. Commonly used integrated photonics platforms, such as silicon nitride, lack sufficient electro-optic coefficients in their waveguide core materials, thus hindering the realization of efficient electro-optic modulation devices. Ferroelectric materials, represented by lithium niobate, exhibit excellent linear electro-optic effects (electro-optic coefficient ro). 33 Lithium niobate (LiNiO) offers advantages such as a high power density (30.8 pm / V) and a wide optical transparency window (0.25~5.3 µm). However, it is not easy to pattern lithium niobate to form waveguide cores with low-roughness sidewalls. Therefore, researchers have developed a composite waveguide core by heterogeneously integrating lithium niobate thin films to achieve low-power, high-frequency electro-optic modulation on silicon nitride photonics platforms, while avoiding the etching of lithium niobate.

[0003] The refractive index of silicon nitride waveguide cores with low propagation loss is typically lower than that of lithium niobate. Therefore, one challenge in heterogeneous integration of lithium niobate on silicon nitride photonics platforms is achieving low optical field transition loss between silicon nitride waveguide cores and silicon nitride-lithium niobate composite waveguide cores. Existing technologies include:

[0004] 1. A horizontal conical structure is formed on the lithium niobate thin film at both ends of the silicon nitride-lithium niobate composite waveguide core to achieve optical field transition; 2. Multiple steps are formed on the lithium niobate thin films at both ends of the silicon nitride-lithium niobate composite waveguide core to achieve optical field transition; 3. Set waveguide cores with a higher refractive index than lithium niobate at both ends of the silicon nitride-lithium niobate composite waveguide core, such as silicon-rich silicon nitride or silicon. The optical field first transitions from the composite waveguide core or silicon nitride waveguide core to the high-refractive-index waveguide core, and then to the silicon nitride waveguide core or composite waveguide core; or the high-refractive-index waveguide core replaces silicon nitride and forms a composite waveguide core with the lithium niobate thin film. 4. A third material (such as non-stoichiometric silicon nitride) is used at both ends of the lithium niobate single crystal thin film along the direction of the silicon nitride waveguide core to form a slope structure to achieve optical field transition (patent application CN117572673A).

[0005] For prior art 1, when integrating lithium niobate onto a silicon nitride platform via micro-transfer printing, high alignment accuracy between the horizontally tapered structure of the lithium niobate thin film and the silicon nitride waveguide core is required to achieve low transition loss, increasing the process complexity. For prior art 2, multiple dry etching processes are required for lithium niobate, which is relatively difficult and does not easily yield a low-roughness stepped surface. Furthermore, it is incompatible with CMOS process equipment due to potential contamination issues. For prior art 3, silicon-rich silicon nitride has high light absorption loss, and silicon is not suitable for visible light. Applications require materials and films other than silicon nitride and lithium niobate, increasing the structural and process complexity of the device. For existing technology 4, since the refractive index of the third material cannot be made completely consistent with that of lithium niobate, when the light field passes through the interface between the third material and lithium niobate above the waveguide core, a certain amount of light scattering loss will occur. In addition, the third material (such as non-stoichiometric silicon nitride) itself may introduce a certain amount of light absorption loss, thereby greatly reducing the reduction of light field transition loss brought about by the slope structure (i.e., the transition loss is reduced, but new scattering loss and absorption loss are introduced). Summary of the Invention

[0006] In view of this, embodiments of this application provide an electro-optic material thin film substrate, an electro-optic modulation device, and a fabrication method. A thickness gradient structure is formed on the lithium niobate thin film at both ends of the silicon nitride-lithium niobate composite waveguide core. This can achieve a low-loss optical field transition between the silicon nitride waveguide core and the silicon nitride-lithium niobate composite waveguide core, while avoiding high-precision alignment bonding between lithium niobate and the silicon nitride waveguide core. It eliminates or reduces the need for patterning processes of lithium niobate and eliminates the need to introduce high-refractive-index materials, thereby reducing the difficulty of the process and the complexity of the device structure.

[0007] In a first aspect, embodiments of this application provide an electro-optic material thin film substrate, comprising: First substrate; The second bonding layer is located on the upper side of the first substrate; The first bonding layer is located above the second bonding layer, and the first bonding layer is provided with at least one set of parallel inverted V-shaped protrusions; An electro-optic material layer is located on the upper side of the first bonding layer. The electro-optic material layer forms a slope at the position corresponding to the inverted V-shaped protrusion, and the electro-optic material layer forms a mesa at the position corresponding to the area between two adjacent inverted V-shaped protrusions in the same group.

[0008] According to one specific implementation of this application, the top of the inverted V-shaped protrusion has a pointed structure, and the electro-optic material layer completely covers the first bonding layer; or, The top of the inverted V-shaped protrusion is a platform structure, which is exposed on the surface of the electro-optic material layer and is flush with the surface of the electro-optic material layer.

[0009] According to one specific implementation of the embodiments of this application, the slope of the electro-optic material layer is set to change linearly or non-linearly.

[0010] According to a specific implementation of an embodiment of this application, the first bonding layer is provided with multiple sets of parallel inverted V-shaped protrusions, and every two sets of inverted V-shaped protrusions intersect each other.

[0011] According to a specific implementation of this application, the target thickness of the electro-optic material layer mesa is 0.1~1μm, the thickness between the surface of the first bonding layer and the electro-optic material layer mesa is 0.1~5μm, the thickness of the second bonding layer is 0~1μm, and the length of the projection of the slope of the electro-optic material layer on the horizontal plane is 5~300μm.

[0012] Secondly, embodiments of this application also provide an electro-optic modulation device, comprising: Second substrate; The lower cladding layer is located on the upper side of the second substrate; Waveguide core, located on the upper side of the lower cladding; The third bonding layer covers the surface of the waveguide core, the side surface of the waveguide core, and the surface of the lower cladding; An electro-optic material thin film wafer is formed by patterning, cutting and removing a first substrate from an electro-optic material thin film substrate as described in any embodiment of the first aspect. The electro-optic material thin film wafer includes at least one electro-optic material layer mesa and a pair of electro-optic material layer slopes located on both sides of the electro-optic material layer mesa. The electro-optic material layer is bonded to a third bonding layer. The electro-optic material layer is located above at least one waveguide core. The electro-optic material layer slopes and the waveguide cores are projected and overlap on the second substrate. The electrodes are located on the side of the second bonding layer away from the first bonding layer. The electrodes are located on both sides of the waveguide core, and at least part of the length of the electrodes is within the length range of the overlapping portion of the projection of the waveguide core and the electro-optic material layer mesa on the second substrate.

[0013] According to a specific implementation of this application, the thickness of the lower cladding layer is 2~20μm, the thickness of the third bonding layer covering the waveguide core surface is 10~200nm, the spacing between two adjacent electrodes is 4~10μm, the electrode thickness is 0.5~2μm, and the electrode width is 5~200μm.

[0014] Thirdly, embodiments of this application provide a method for fabricating an electro-optic modulation device as described in any embodiment of the second aspect, comprising: Ion implantation is performed on one side of the electro-optic material wafer to form a damage layer inside the electro-optic material wafer and an electro-optic material layer formed by the damage layer. At least one set of parallel V-shaped grooves are formed on the surface of the electro-optic material layer away from the electro-optic material wafer. The sidewalls of the V-shaped grooves form the slope of the electro-optic material layer, and the area between two adjacent V-shaped grooves in the same set forms the mesa of the electro-optic material layer. A first bonding layer is formed on the side of the electro-optic material layer away from the electro-optic material wafer; A first substrate having a second bonding layer on one side surface is provided, wherein the second bonding layer is bonded to the surface of the first bonding layer to form an assembly; The assembly is annealed, and the electro-optic material wafer is peeled off along the damaged layer to obtain an electro-optic material thin film substrate. The electro-optic material thin film substrate is then annealed and chemically mechanically polished. The polished electro-optic material thin film substrate is patterned to form trenches, with the patterned position corresponding to the bottom end of the V-shaped groove, thus dividing the electro-optic material layer into an array; The first substrate is cut along the trench to form a small electro-optic material thin film substrate piece; A second substrate is provided, on the surface of which a lower cladding layer, a waveguide core, and a third bonding layer are sequentially formed, and the third bonding layer covers the surface of the waveguide core, the side surface of the waveguide core, and the surface of the lower cladding layer. The electro-optic material layer of the electro-optic material thin film substrate is bonded to the surface of the third bonding layer; After removing the first substrate, the electro-optic material layer, the first bonding layer and the second bonding layer constitute an electro-optic material thin film sheet; Electrodes are formed on both sides of the waveguide core.

[0015] According to a specific implementation of an embodiment of this application, the chemical mechanical polishing includes: The surface of the electro-optic material layer is chemically and mechanically polished until the thickness of the electro-optic material layer mesa reaches the target thickness, exposing the first bonding layer or not exposing the first bonding layer.

[0016] According to a specific implementation of an embodiment of this application, the step of patterning the polished electro-optic material thin film substrate to form trenches includes: The polished electro-optic material layer, the first bonding layer, and / or the second bonding layer are patterned to form trenches.

[0017] Beneficial effects: The electro-optic material thin film substrate, electro-optic modulation device, and fabrication method in this application embodiment form an electro-optic material thin film substrate with at least one pair of slope structures in its electro-optic material layer. An electro-optic modulation device with low insertion loss is fabricated using this substrate. Specifically, compared to existing technologies that utilize horizontal conical structures formed on electro-optic material thin films (such as lithium niobate) to achieve optical field transition, this solution does not require high alignment precision during electro-optic material layer bonding, reducing process difficulty. Compared to existing technologies that form multiple steps on electro-optic material thin films (such as lithium niobate) to achieve optical field transition, this solution requires only one or no etching of the electro-optic material layer, reducing process complexity and improving the device's CMOS process compatibility. Compared to existing technologies that introduce waveguide cores, transition waveguide cores (materials other than the electro-optic material layer), auxiliary waveguide cores, and waveguide core-electro-optic material layer composite waveguide cores for optical field transition, this solution does not require the introduction of a transition waveguide core, avoiding problems such as increased propagation loss, increased film layers and process steps, and increased device complexity caused by the transition waveguide core. This scheme utilizes the slope structure of the electro-optic material layer to achieve efficient optical field transition between waveguide cores and waveguide core-electro-optic material layer composite waveguide cores, effectively reducing the insertion loss of electro-optic modulation devices. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A cross-sectional view of an electro-optic material wafer ion implantation according to an embodiment of the present invention; Figure 2 A top view of a set of V-grooves prepared for an electro-optic material layer according to an embodiment of the present invention; Figure 3 for Figure 2 Cross-sectional view at point AA; Figure 4 A top view of two sets of V-grooves prepared for an electro-optic material layer according to an embodiment of the present invention; Figure 5 A cross-sectional view of the preparation of the first bonding layer according to an embodiment of the present invention; Figure 6 A cross-sectional view of a first substrate having a second bonding layer according to an embodiment of the present invention; Figure 7 A cross-sectional view of the bonding between the first bonding layer and the second bonding layer according to an embodiment of the present invention; Figure 8 This is a cross-sectional view of the electro-optic material wafer peeling when the first bonding layer is not exposed, according to an embodiment of the present invention. Figure 9 This is a cross-sectional view of the electro-optic material wafer peeling when the first bonding layer is exposed according to an embodiment of the present invention; Figure 10 A top view of the electro-optic material wafer peeling when the first bonding layer is exposed according to an embodiment of the present invention; Figure 11 A top view of an electro-optic material wafer with two sets of V-grooves being peeled off when the first bonding layer is exposed according to an embodiment of the present invention; Figure 12 This is a graphical cross-sectional view of the first bonding layer not being exposed according to an embodiment of the present invention; Figure 13 This is a graphical top view of the present invention when the first bonding layer is not exposed; Figure 14 A graphical top view of a first bonding layer without exposure according to an embodiment of the present invention, showing two sets of V-grooves; Figure 15 A graphical cross-sectional view of the first bonding layer exposed according to an embodiment of the present invention; Figure 16 A graphical top view of the first bonding layer when it is exposed according to an embodiment of the present invention; Figure 17 A graphical top view of the first bonding layer with two sets of V-grooves when exposed according to an embodiment of the present invention; Figure 18 A cross-sectional view of a small electro-optic material thin film substrate according to an embodiment of the present invention; Figure 19 A cross-sectional view of a second substrate according to an embodiment of the present invention; Figure 20 A cross-sectional view of the bonding between an electro-optic material thin film substrate chip and a second substrate according to an embodiment of the present invention; Figure 21 A top view of the first substrate removed according to an embodiment of the present invention; Figure 22 for Figure 21 Cross-sectional view at point C; Figure 23 for Figure 21 Cross-sectional view at DD in the middle; Figure 24 A cross-sectional view of electrode fabrication according to an embodiment of the present invention; Figure 25 A top view of electrode fabrication according to an embodiment of the present invention.

[0020] In the figure: 1. Electro-optic material layer; 101. Electro-optic material layer slope; 102. Electro-optic material layer mesa; 2. Damage layer; 3. Electro-optic material wafer; 4. First bonding layer; 5. Second bonding layer; 6. First substrate; 7. Third bonding layer; 8. Waveguide core; 9. Lower cladding layer; 10. Second substrate; 11. Electrode. Detailed Implementation

[0021] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0022] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0024] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0026] In a first aspect, embodiments of this application provide an electro-optic material thin film substrate, referring to... Figures 8 to 11 ,include: First substrate 6; The second bonding layer 5 is located on the upper side of the first substrate 6; The first bonding layer 4 is located above the second bonding layer 5, and the first bonding layer 4 is provided with at least one set of parallel inverted V-shaped protrusions. Electro-optic material layer 1 is located on the upper side of the first bonding layer 4. Electro-optic material layer 1 forms an electro-optic material layer slope 101 at the position corresponding to the inverted V-shaped protrusion. Electro-optic material layer 1 forms an electro-optic material layer platform 102 at the position corresponding to the area between two adjacent inverted V-shaped protrusions in the same group.

[0027] In this embodiment, the slope and mesa structure formed by the electro-optic material layer 1 are adapted to the subsequent electrode 11 fabrication process, reducing the non-uniformity of the modulation electric field and optimizing the electro-optic modulation performance of the final device. The first bonding layer 4 provides support for the slope structure of the electro-optic material layer 1 during the chemical mechanical polishing process, preventing the chemical mechanical polishing process from damaging the slope structure.

[0028] Furthermore, refer to Figure 8 The inverted V-shaped protrusion has a pointed tip, and the electro-optic material layer 1 completely covers the first bonding layer 4; or, Reference Figure 9 The top of the inverted V-shaped protrusion is a platform structure, which is exposed on the surface of the electro-optic material layer 1 and is flush with the surface of the electro-optic material layer 1.

[0029] Furthermore, the slope of the electro-optic material layer slope 101 is set to vary linearly or non-linearly.

[0030] Furthermore, refer to Figure 11 The first bonding layer 4 has multiple sets of parallel inverted V-shaped protrusions, with each pair of inverted V-shaped protrusions intersecting.

[0031] In specific implementation, the electro-optic material layer 1 corresponding to the inverted V-shaped protrusion of the first bonding layer 4 is a V-shaped groove. The slope of the V-shaped groove is the slope 101 of the electro-optic material layer. The electro-optic material layer 1 is provided with multiple sets of parallel V-shaped grooves. Every two sets of V-shaped grooves intersect. The slope, depth, and width of the slope of each set of V-shaped grooves can be the same or different. The width of the V-shaped groove is the projection length of the V-shaped groove on the horizontal plane.

[0032] Furthermore, the target thickness of the electro-optic material layer mesa 102 is 0.1~1μm, the thickness between the surface of the first bonding layer 4 and the electro-optic material layer mesa 102 is 0.1~5μm, the thickness of the second bonding layer 5 is 0~1μm, and the length of the single-sided electro-optic material layer slope 101 projected onto the horizontal plane is 5~300μm.

[0033] Secondly, embodiments of this application also provide an electro-optic modulation device, comprising: Second substrate 10; The lower cladding layer 9 is located on the upper side of the second substrate 10; Waveguide core 8 is located on the upper side of the lower cladding layer 9; The third bonding layer 7 covers the surface of the waveguide core 8, the side of the waveguide core 8, and the surface of the lower cladding layer 9. An electro-optic material thin film wafer is formed by patterning, cutting and removing the first substrate 6 of the electro-optic material thin film substrate as described in any embodiment of the first aspect. The electro-optic material thin film wafer includes at least one electro-optic material layer mesa 102 and a pair of electro-optic material layer slopes 101 located on both sides of the electro-optic material layer mesa 102. The electro-optic material layer 1 is bonded to the third bonding layer 7. The electro-optic material layer 1 is located above at least one waveguide core 8. The electro-optic material layer slope 101 and the waveguide core 8 are projected and overlapped on the second substrate 10. Electrode 11 is located on the side of the second bonding layer 5 away from the first bonding layer 4. Electrode 11 is located on both sides of the waveguide core 8, and at least part of the length of electrode 11 is within the length range of the overlapping portion of the projection of the waveguide core 8 and the electro-optic material layer mesa 102 on the second substrate 10.

[0034] In this embodiment, by projecting the slope of the electro-optic material layer 1 onto the waveguide core 8, and with the electrode 11 positioned within the length of the projected overlap, the modulation electric field can better penetrate the composite waveguide core region formed by the waveguide core 8 and the electro-optic material layer mesa 102, thereby improving the modulation efficiency of the electric field on the optical signal. At the same time, the third bonding layer 7 can achieve stable bonding between the electro-optic material layer 1 and the lower cladding layer 9 and the waveguide core 8, ensuring the stability of the device structure and reducing the impact of interface defects on device performance.

[0035] Furthermore, the thickness of the lower cladding layer 9 is 2~20μm, the thickness of the third bonding layer 7 covering the surface of the waveguide core 8 is 10~200nm, the spacing between two adjacent electrodes 11 is 4~10μm, the thickness of the electrode 11 is 0.5~2μm, and the width of the electrode 11 is 5~200μm.

[0036] Thirdly, embodiments of this application provide a method for fabricating an electro-optic modulation device as described in any embodiment of the second aspect, comprising: Ion implantation is performed on one side of the electro-optic material wafer 3 to form a damage layer 2 located inside the electro-optic material wafer 3 and an electro-optic material layer 1 formed by the damage layer 2. At least one set of parallel V-shaped grooves are formed on the surface of the electro-optic material layer 1 away from the electro-optic material wafer 3. The sidewalls of the V-shaped grooves form the electro-optic material layer slope 101, and the area between two adjacent V-shaped grooves in the same set forms the electro-optic material layer mesa 102. A first bonding layer 4 is formed on the side of the electro-optic material layer 1 away from the electro-optic material wafer 3; A first substrate 6 is provided with a second bonding layer 5 on one side surface, and the second bonding layer 5 is bonded to the surface of the first bonding layer 4 to form an assembly; The assembly is annealed, and the electro-optic material wafer 3 is peeled off along the damaged layer 2 to obtain the electro-optic material thin film substrate. The electro-optic material thin film substrate is then annealed and chemically mechanically polished. The polished electro-optic material thin film substrate is patterned to form trenches, with the patterned position corresponding to the bottom of the V-shaped groove, dividing the electro-optic material layer 1 into an array; The first substrate 6 is cut along the trench to form a small electro-optic material thin film substrate piece; A second substrate 10 is provided, and a lower cladding layer 9, a waveguide core 8 and a third bonding layer 7 are sequentially formed on the surface of the second substrate 10. The third bonding layer 7 covers the surface of the waveguide core 8, the side surface of the waveguide core 8 and the surface of the lower cladding layer 9. The electro-optic material layer 1 of the electro-optic material thin film substrate is surface-bonded to the third bonding layer 7; After removing the first substrate 6, the electro-optic material layer 1, the first bonding layer 4, and the second bonding layer 5 form an electro-optic material thin film sheet. Electrodes 11 are formed on both sides of the waveguide core 8.

[0037] In one embodiment, the chemical mechanical polishing includes: The surface of the electro-optic material layer 1 is chemically and mechanically polished until the thickness of the electro-optic material layer mesa 102 reaches the target thickness, exposing the first bonding layer 4 or not exposing the first bonding layer 4.

[0038] In one embodiment, patterning the polished electro-optic material thin film substrate to form trenches includes: The polished electro-optic material layer 1, the first bonding layer 4 and / or the second bonding layer 5 are patterned to form trenches.

[0039] In one embodiment, the method for preparing the electro-optic material thin film substrate of this application is described in detail, specifically including the following steps: Reference Figure 1 Ion implantation is performed on one side of the electro-optic material wafer 3 to form a damage layer 2 near a certain depth on the surface of one side of the electro-optic material wafer 3. The surface of the electro-optic material wafer 3 on the side of the damage layer 2 is divided to form an electro-optic material layer 1. The material of electro-optic material wafer 3 can be lithium niobate, lithium tantalate, or barium titanate, etc.; the implanted ions can be H... + or He + Ions, implantation dose of 5 × 10 15 ~5×10 17 / cm2 The depth of the second damaged layer is 0.5~2μm.

[0040] Reference Figures 2 to 4 At least one set of parallel V-grooves is formed on one side of the electro-optic material layer 1 of the electro-optic material wafer 3; preferably, the bottom of the V-grooves is not deeper than the damage layer 2, and the slope of the V-groove can be linearly or non-linearly varied, with the projection length of a single slope on the horizontal plane being 5~300μm. The two sets of V-grooves intersect, such as... Figure 4 As shown, the slope, depth, and width of the slopes of the two sets of V-shaped grooves can be the same or different.

[0041] Specifically, the arrangement of the V-groove determines the shape and slope position of the array unit of the electro-optic material layer 1. The selection of the shape and slope position of the array unit of the electro-optic material layer 1 is based on the orientation of the waveguide core 8. It should be ensured that the waveguide core 8 passes under the slope when passing under the array unit of the electro-optic material layer 1. The slope 101 of the electro-optic material layer is used to realize the efficient optical field transition between the waveguide core 8 and the waveguide core 8-electro-optic material layer 1 composite waveguide core, thereby reducing the insertion loss of the electro-optic modulation device.

[0042] Reference Figure 5 A first bonding layer 4 is formed on the upper side of the electro-optic material layer 1 of the electro-optic material wafer 3. The material of the first bonding layer 4 can be silicon dioxide, aluminum oxide, bonding adhesive, or a combination thereof. The side of the first bonding layer 4 away from the electro-optic material wafer 3 has a flat surface. The thickness of the first bonding layer 4 at the position corresponding to the mesa 102 of the electro-optic material layer is 0.1~5μm.

[0043] Reference Figure 6 and Figure 7 A first substrate 6 is provided with a second bonding layer 5 on one side surface. The first bonding layer 4 and the second bonding layer 5 are surface-to-surface bonded together, so that the electro-optic material wafer 3 and the first substrate 6 form a combination. The material of the first substrate 6 can be silicon or quartz, etc., and the material of the second bonding layer 5 can be silicon dioxide, aluminum oxide, bonding adhesive, etc. or a combination thereof. The side of the second bonding layer 5 away from the first substrate 6 has a flat surface, and the thickness of the second bonding layer 5 is 0~1μm.

[0044] The assembly is annealed to peel off the electro-optic material wafer 3 along the damaged layer 2, while the electro-optic material layer 1 remains on the first substrate 6, resulting in an electro-optic material thin film substrate. The electro-optic material thin film substrate is then annealed to repair the lattice damage caused by the ion-implanted electro-optic material layer 1. The surface of the electro-optic material layer 1 is then chemically and mechanically polished until the thickness of the electro-optic material layer mesa 102 reaches the target thickness. The target thickness of the electro-optic material layer mesa 102 is 0.1~1μm.

[0045] Optionally, after the electro-optic material layer mesa 102 reaches the target thickness, the first bonding layer 4 is exposed (e.g., Figure 9 and Figure 10 Or the first bonding layer 4 is not exposed (e.g.) Figure 8 ); Figure 11 This diagram illustrates the setup of two sets of V-grooves, exposing the first bonding layer 4. The two sets of V-grooves are arranged vertically. The first bonding layer 4 provides support to the slope structure of the electro-optic material layer 1 during the chemical mechanical polishing (CMP) process, preventing damage to the slope structure from the CMP process.

[0046] In one embodiment, the method for fabricating the electro-optic modulation device of this application is described in detail, including the following steps: The obtained electro-optic material thin film substrate is patterned, including patterning the electro-optic material layer 1 and / or the first bonding layer 4 and / or the second bonding layer 5, dividing the electro-optic material layer 1 into array units; preferably, a portion of the first substrate 6 is exposed after patterning. Electro-optic materials are generally incompatible with CMOS processes, and this method can avoid etching the electro-optic material layer 1. Figure 12 and Figure 13 As shown, the first bonding layer 4 is not exposed and a set of V-grooves are provided; as Figure 14 As shown, this illustrates a case where the first bonding layer 4 is not exposed and two sets of V-grooves are provided; as Figure 15 and Figure 16 As shown, this illustrates the case where the first bonding layer 4 is exposed and a set of V-grooves are provided; as Figure 17 As shown, the first bonding layer 4 is exposed and two sets of V-grooves are provided.

[0047] It should be noted that the patterned position needs to be aligned with the center of the inverted V-shaped protrusion of the first bonding layer 4. The slope structure of the electro-optic material layer 1 array unit obtained at this position is more uniform. The more the patterned trench position deviates from the center of the inverted V-shaped protrusion of the first bonding layer 4, the greater the difference in the initial slope thickness (end thickness) and slope length of the electro-optic material layer 1 array unit on both sides of the trench. Moreover, a thicker initial slope thickness is detrimental to the low-loss optical field transition between the waveguide core 8 and the waveguide core 8-electro-optic material layer 1 composite waveguide core.

[0048] Furthermore, the width of the patterned trench is smaller than the width of the exposed first bonding layer 4 and lies within the width range of the exposed first bonding layer 4. In the case of the exposed first bonding layer 4, the slope thickness of the electro-optic material layer 1 array unit transitions from 0 to mesa thickness, which is more advantageous for the low-loss optical field transition between the waveguide core 8 and the waveguide core 8-electro-optic material layer 1 composite waveguide core (compared to the slope thickness of the electro-optic material layer 1 array unit transitioning from a non-zero slope thickness to a mesa thickness). Therefore, the width of the patterned trench between the electro-optic material layer slopes 101 is smaller than the width of the exposed first bonding layer 4 and lies within the width range of the exposed first bonding layer 4, ensuring that the structure of the electro-optic material layer 1 array unit transitioning from 0 to mesa thickness is not disrupted.

[0049] Reference Figure 18 The first substrate 6 is cut along the trench positions of the electro-optic material layer 1, the first bonding layer 4 and the second bonding layer 5 to form an electro-optic material thin film substrate piece. Each electro-optic material thin film substrate piece includes at least one electro-optic material layer 1 array unit, and each electro-optic material layer 1 array unit has at least one pair of slope structures.

[0050] Reference Figure 19 A second substrate 10 is provided, on the surface of which a lower cladding layer 9, a waveguide core 8, and a third bonding layer 7 are sequentially formed. The third bonding layer 7 covers the surface of the waveguide core 8, the side surface of the waveguide core 8, and the surface of the lower cladding layer 9. The material of the second substrate 10 is Si, etc.; the material of the lower cladding layer 9 is silicon dioxide with a thickness of 2~20μm; the material of the waveguide core 8 is silicon nitride or silicon, etc.; the material of the third bonding layer 7 can be silicon dioxide, alumina, bonding adhesive, or a combination thereof. The side of the third bonding layer 7 away from the second substrate 10 has a flat surface, and the thickness of the third bonding layer 7 on the surface of the waveguide core 8 is 10~200nm.

[0051] Reference Figure 20 One side surface of the electro-optic material layer 1 of the electro-optic material thin film substrate is bonded to the surface of the third bonding layer 7 of the second substrate 10. The electro-optic material layer 1 is located above at least one waveguide core 8. At least one pair of slope structures of the electro-optic material layer 1 overlaps with the projection of the waveguide core 8 on the second substrate 10.

[0052] Reference Figures 21 to 23 Remove the first substrate 6, and the electro-optic material layer 1, the first bonding layer 4 and the second bonding layer 5 form an electro-optic material thin film.

[0053] Reference Figure 24 and Figure 25Electrodes 11 are formed on both sides of the waveguide core 8. At least a portion of the length of the electrodes 11 lies within the overlapping length of the projections of the waveguide core 8 and the electro-optic material layer mesa 102 onto the second substrate 10. Specifically, the electrodes 11 are located on both sides of the waveguide core 8, and the electro-optic material layer mesa 102 is located above the waveguide core 8 at this location. It can be understood that the waveguide core 8 and the electro-optic material layer mesa 102 combine to form a composite waveguide core (the electro-optic material layer slope 101 serves as a transition of the optical field between the composite waveguide core and the waveguide core 8), and at least a portion of the electrodes 11 should be located on both sides of the composite waveguide core.

[0054] The electrode 11 can be made of aluminum, gold or copper, etc. The spacing between adjacent electrodes 11 is 4~10μm, the thickness of electrode 11 is 0.5~2μm, and the width of electrode 11 is 5~200μm.

[0055] The embodiments provided by the present invention include an electro-optic material thin film substrate comprising at least one electro-optic material layer 1 array unit, the electro-optic material layer 1 array unit having at least one pair of slope structures, and an electro-optic modulation device is fabricated based on the electro-optic material thin film substrate, wherein the at least one pair of slope structures of the electro-optic material layer 1 array unit overlaps with the waveguide core 8 projected onto the second substrate 10, and the slope structure of the electro-optic material layer 1 can be used to achieve efficient optical field transition between the waveguide core 8 and the waveguide core 8-electro-optic material layer 1 composite waveguide core, thereby reducing the insertion loss of the electro-optic modulation device.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electro-optic material thin film substrate, characterized in that, include: First substrate (6); The second bonding layer (5) is located on the upper side of the first substrate (6); The first bonding layer (4) is located above the second bonding layer (5), and the first bonding layer (4) is provided with at least one set of parallel inverted V-shaped protrusions; An electro-optic material layer (1) is located on the upper side of the first bonding layer (4). The electro-optic material layer (1) forms an electro-optic material layer slope (101) at the position corresponding to the inverted V-shaped protrusion. The electro-optic material layer (1) forms an electro-optic material layer platform (102) at the position corresponding to the area between two adjacent inverted V-shaped protrusions in the same group.

2. The electro-optic material thin film substrate according to claim 1, characterized in that, The inverted V-shaped protrusion has a pointed top structure, and the electro-optic material layer (1) completely covers the first bonding layer (4); or, The top of the inverted V-shaped protrusion is a platform structure, which is exposed on the surface of the electro-optic material layer (1) and is flush with the surface of the electro-optic material layer (1).

3. The electro-optic material thin film substrate according to claim 1, characterized in that, The slope of the electro-optic material layer slope (101) is set to either linear or nonlinear variation.

4. The electro-optic material thin film substrate according to claim 1, characterized in that, The first bonding layer (4) has multiple sets of parallel inverted V-shaped protrusions, with each pair of inverted V-shaped protrusions intersecting.

5. The electro-optic material thin film substrate according to claim 1, characterized in that, The target thickness of the electro-optic material layer mesa (102) is 0.1~1μm, the thickness between the surface of the first bonding layer (4) and the electro-optic material layer mesa (102) is 0.1~5μm, the thickness of the second bonding layer (5) is 0~1μm, and the length of the single-sided electro-optic material layer slope (101) projected onto the horizontal plane is 5~300μm.

6. An electro-optic modulation device, characterized in that, include: Second substrate (10); The lower cladding layer (9) is located on the upper side of the second substrate (10); Waveguide core (8) is located on the upper side of the lower cladding (9); The third bonding layer (7) covers the surface of the waveguide core (8), the side of the waveguide core (8), and the surface of the lower cladding layer (9); An electro-optic material thin film wafer is formed by patterning, cutting and removing a first substrate (6) of an electro-optic material thin film substrate as described in any one of claims 1-5. The electro-optic material thin film wafer includes at least one electro-optic material layer mesa (102) and a pair of electro-optic material layer slopes (101) located on both sides of the electro-optic material layer mesa (102). The electro-optic material layer (1) is bonded to a third bonding layer (7). The electro-optic material layer (1) is located above at least one waveguide core (8). The electro-optic material layer slopes (101) and the waveguide core (8) are projected and overlapped on a second substrate (10). Electrode (11) is located on the side of the second bonding layer (5) away from the first bonding layer (4). Electrode (11) is located on both sides of the waveguide core (8), and at least part of the length of electrode (11) is within the length range of the overlapping portion of the projection of the waveguide core (8) and the electro-optic material layer mesa (102) on the second substrate (10).

7. The electro-optic modulation device according to claim 6, characterized in that, The thickness of the lower cladding (9) is 2~20μm, the thickness of the third bonding layer (7) covering the surface of the waveguide core (8) is 10~200nm, the spacing between two adjacent electrodes (11) is 4~10μm, the thickness of the electrode (11) is 0.5~2μm, and the width of the electrode (11) is 5~200μm.

8. A method for fabricating an electro-optic modulation device as described in claim 6 or 7, characterized in that, include: Ion implantation is performed on one side of the electro-optic material wafer (3) to form a damage layer (2) inside the electro-optic material wafer (3) and an electro-optic material layer (1) formed by the damage layer (2). At least one set of parallel V-shaped grooves are formed on the surface of the electro-optic material layer (1) away from the electro-optic material wafer (3). The sidewalls of the V-shaped grooves form the electro-optic material layer slope (101), and the area between two adjacent V-shaped grooves in the same set forms the electro-optic material layer mesa (102). A first bonding layer (4) is formed on the side of the electro-optic material layer (1) away from the electro-optic material wafer (3); A first substrate (6) is provided with a second bonding layer (5) on one side surface, the second bonding layer (5) being bonded to the surface of the first bonding layer (4) to form an assembly; The assembly was annealed, and the electro-optic material wafer (3) was peeled off along the damaged layer (2) to obtain the electro-optic material thin film substrate. The electro-optic material thin film substrate was then annealed and chemically and mechanically polished. The polished electro-optic material thin film substrate is patterned to form trenches, with the patterned position corresponding to the bottom of the V-shaped groove, and the electro-optic material layer (1) is divided into an array; The first substrate (6) is cut along the trench to form a small electro-optic material thin film substrate piece; A second substrate (10) is provided, and a lower cladding layer (9), a waveguide core (8) and a third bonding layer (7) are sequentially formed on the surface of the second substrate (10). The third bonding layer (7) covers the surface of the waveguide core (8), the side of the waveguide core (8) and the surface of the lower cladding layer (9). The electro-optic material layer (1) of the electro-optic material thin film substrate is bonded to the surface of the third bonding layer (7); After removing the first substrate (6), the electro-optic material layer (1), the first bonding layer (4), and the second bonding layer (5) form an electro-optic material thin film sheet; Electrodes (11) are formed on both sides of the waveguide core (8).

9. The preparation method according to claim 8, characterized in that, The chemical mechanical polishing includes: The surface of the electro-optic material layer (1) is chemically and mechanically polished until the thickness of the electro-optic material layer mesa (102) reaches the target thickness, exposing the first bonding layer (4) or not exposing the first bonding layer (4).

10. The preparation method according to claim 8, characterized in that, The process of patterning trenches on the polished electro-optic material thin film substrate includes: The polished electro-optic material layer (1), the first bonding layer (4) and / or the second bonding layer (5) are patterned to form trenches.

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