A resonant device and a method of manufacturing the same

Abstract

The application belongs to the technical field of optical communication, and discloses a resonant device and a preparation method thereof. The resonant device comprises an optical waveguide micro-ring resonator and a film bulk acoustic resonator. The film bulk acoustic resonator comprises an upper electrode layer, a piezoelectric material layer and a lower electrode layer. The piezoelectric material layer is located between the upper electrode layer and the lower electrode layer. The optical waveguide micro-ring resonator is embedded in the piezoelectric material layer. The optical waveguide micro-ring resonator is coupled with the film bulk acoustic resonator. The inverse piezoelectric effect of the film bulk acoustic resonator can realize frequency modulation of the optical waveguide micro-ring resonator, and the coupling effect of the two can reach the best. In addition, the piezoelectric material layer in the film bulk acoustic resonator can directly act as a reflection medium of the optical waveguide micro-ring resonator, thereby effectively simplifying the structure.

Description

Technical Field

[0001] This invention belongs to the field of optical communication technology, and more specifically, relates to a resonant device and its fabrication method. Background Technology

[0002] Optical filters are devices that use optical principles to filter signals in the microwave and higher frequency bands. Compared with existing traditional filters, optical filters use light for signal processing, giving them a significant advantage in the high-frequency range. Optical waveguide microring resonators are an important component of optical filters, utilizing the selective diffraction of optical signals by the resonator microrings to achieve filtering functionality.

[0003] The selectivity of an optical waveguide microring resonator to optical signals is determined by the material properties and the resonator geometry. Once fabricated, the wavelength of the optical signal that the optical waveguide microring resonator can select is fixed. Therefore, an external device is needed to tune the optical waveguide microring resonator.

[0004] Thin-film bulk acoustic wave resonators (FCWs) are key components in well-developed RF filters, and like optical waveguide filters, they can be integrated and manufactured on silicon wafers. By coupling the FCW and the optical waveguide microring resonator, electrical signals can control optical signals; however, the coupling effect between the two in current technologies is relatively poor. Summary of the Invention

[0005] This invention provides a resonant device and its fabrication method, which solves the problem of poor coupling effect between the two when using a thin-film bulk acoustic resonator to tune the frequency of an optical waveguide microring resonator in the prior art.

[0006] The present invention provides a resonant device, comprising: an optical waveguide microring resonator and a thin-film bulk acoustic resonator; the thin-film bulk acoustic resonator includes an upper electrode layer, a piezoelectric material layer and a lower electrode layer, the piezoelectric material layer being located between the upper electrode layer and the lower electrode layer; the optical waveguide microring resonator is embedded in the piezoelectric material layer, and the optical waveguide microring resonator is coupled to the thin-film bulk acoustic resonator.

[0007] Preferably, the optical waveguide microring resonator includes a linear waveguide and a circular resonant microring; the optical signal enters from one end of the linear waveguide, generates a resonant signal through the circular resonant microring, and then exits from the other end of the linear waveguide.

[0008] Preferably, the thin-film bulk acoustic resonator further includes a substrate, and a cavity is provided between the substrate and the lower electrode layer; the shape of the core working area of ​​the upper electrode layer and the shape of the core working area of ​​the lower electrode layer are the same polygon, and the core working areas of the upper electrode layer and the core working areas of the lower electrode layer are both covered by the circular resonant microring in the direction perpendicular to the electrode plane.

[0009] Preferably, the piezoelectric material layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, and lead zirconate titanate; the optical waveguide microring resonator is made of silicon or silicon dioxide.

[0010] Preferably, the optical waveguide microring resonator and the piezoelectric material layer have the same height and are seamlessly adjacent.

[0011] Preferably, the piezoelectric material layer has etched slots, and the optical waveguide microring resonator is deposited in the slots.

[0012] This invention provides a method for fabricating a resonant device, comprising the following steps:

[0013] Step 1: Etch a cavity on the substrate of the thin-film bulk acoustic resonator;

[0014] Step 2: Deposit a sacrificial layer to fill the cavity;

[0015] Step 3: Deposit the lower electrode layer;

[0016] Step 4: Deposit a piezoelectric material layer above the lower electrode layer;

[0017] Step 5: Etch a slot in the piezoelectric material layer for embedding the optical waveguide microring resonator;

[0018] Step 6: Deposit the first material used to form the optical waveguide microring resonator;

[0019] Step 7: Remove the first material located above the piezoelectric material layer to form the target structure of the optical waveguide microring resonator;

[0020] Step 8: Deposit the upper electrode layer;

[0021] Step 9: Release the sacrificial layer to obtain the resonant device.

[0022] Preferably, the first material is silicon or silicon dioxide; the target structure of the formed optical waveguide microring resonator includes a linear waveguide and a circular resonant microring.

[0023] Preferably, the piezoelectric material layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, and lead zirconate titanate.

[0024] Preferably, in step 3, a seed layer is deposited before depositing the lower electrode layer, and the lower electrode layer is etched into the desired shape after depositing the lower electrode layer; in step 8, the upper electrode layer is etched into the desired shape after depositing the upper electrode layer, wherein the shape of the core working area of ​​the upper electrode layer and the shape of the core working area of ​​the lower electrode layer are the same polygon, and the core working areas of the upper electrode layer and the core working areas of the lower electrode layer are both covered by the circular resonant microring in the direction perpendicular to the electrode plane; in step 9, the sacrificial layer is released by introducing a corrosive gas.

[0025] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0026] This invention embeds an optical waveguide microring resonator within the piezoelectric material layer of a thin-film bulk acoustic wave (FCAS) resonator. Utilizing the inverse piezoelectric effect of the FCAS resonator, an applied electrical signal alters the vibration state of the FCAS resonator, influencing the refractive state of the optical waveguide and thus enabling frequency modulation of the optical waveguide microring resonator. The coupling between the optical waveguide microring resonator and the FCAS resonator is achieved by placing the microring within the acoustic wave range of the piezoelectric resonator. Generally, the primary operating mode of the FCAS resonator is longitudinal wave in the vertical direction, and the acoustic wave range is mainly above, below, and inside the FCAS resonator's operating area. Since acoustic waves are reflected at the solid-air interface, the acoustic waves transmitted into the air are much weaker than those inside the device. Therefore, to achieve efficient coupling between the optical and acoustic resonators, the air gap between them should be minimized. Compared to the interior of the FCAS resonator, the acoustic waves transmitted above and below the FCAS resonator need to pass through the solid-solid interface between the piezoelectric film and the metal electrodes, resulting in some attenuation. Furthermore, if the optical microring is placed on the upper and lower surfaces of the acoustic resonator, the weight of the microring itself and the corresponding optical reflecting medium will significantly affect the operating frequency of the acoustic resonator. Based on these considerations, this invention utilizes the simple effective working structure of the microring resonator by embedding the optical waveguide microring resonator within the piezoelectric material layer of the thin-film bulk acoustic resonator. This not only optimizes the coupling effect between the two but also allows the piezoelectric material layer in the thin-film bulk acoustic resonator to directly serve as the reflecting medium of the optical waveguide microring resonator, thereby effectively simplifying the structure. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a resonant device provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a flowchart illustrating the fabrication process of a resonant device according to Embodiment 2 of the present invention. Detailed Implementation

[0029] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0030] Example 1:

[0031] Example 1 provides a resonant device, see [link to example]. Figure 1 The device includes an optical waveguide microring resonator and a thin-film bulk acoustic resonator. The thin-film bulk acoustic resonator includes an upper electrode layer 2-1, a piezoelectric material layer 2-2, and a lower electrode layer 2-3, wherein the piezoelectric material layer 2-2 is located between the upper electrode layer 2-1 and the lower electrode layer 2-3. The optical waveguide microring resonator is embedded in the piezoelectric material layer 2-2 and is coupled to the thin-film bulk acoustic resonator.

[0032] The optical waveguide microring resonator includes a linear waveguide 1-1 and a circular resonant microring 1-2. The optical signal enters from one end of the linear waveguide 1-1, generates a resonant signal through the circular resonant microring 1-2, and then exits from the other end of the linear waveguide 1-1.

[0033] Furthermore, the thin-film bulk acoustic resonator also includes a substrate 2-4, with a cavity between the substrate 2-4 and the lower electrode layer 2-3. That is, the basic structure of the thin-film bulk acoustic resonator is a sandwich structure, which can be understood as follows: from top to bottom, the structure of the thin-film bulk acoustic resonator consists of the upper electrode layer 2-1, the piezoelectric material layer 2-2 (i.e., the piezoelectric thin film), the lower electrode layer 2-3, the cavity, and the substrate 2-4. The core working area (i.e., the main working area or effective working area) of the thin-film bulk acoustic resonator is an irregular pentagon or other effective shape. A specific frequency electrical signal is input from the upper and lower electrodes, and the piezoelectric thin film generates vibrating sound waves.

[0034] Specifically, the core working area of ​​the upper electrode layer 2-1 and the core working area of ​​the lower electrode layer 2-3 are both polygons, and the core working areas of the upper electrode layer 2-1 and the lower electrode layer 2-3 both cover the circular resonant microring 1-2 in a direction perpendicular to the electrode plane.

[0035] The piezoelectric material layer 2-2 is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, and lead zirconate titanate; the optical waveguide microring resonator is made of silicon or silicon dioxide.

[0036] Specifically, the optical waveguide microring resonator and the piezoelectric material layer 2-2 have the same height and are seamlessly adjacent. For example, the piezoelectric material layer 2-2 has etched slots, and the optical waveguide microring resonator is deposited in the slots.

[0037] Example 1 provides a resonant device in which an optical waveguide microring resonator is placed inside and coupled to a thin-film bulk acoustic wave resonator. Example 1 enables frequency modulation of the optical waveguide microring resonator based on the thin-film bulk acoustic wave resonator. When a driving source of a specific carrier frequency is applied to the thin-film bulk acoustic wave resonator, the resonator generates ultrasonic waves of the same frequency within the piezoelectric film. These waves are transmitted to the optical medium embedded within the piezoelectric film, causing periodic changes in the refractive index of the optical medium. As the light beam passes through the optical medium, diffraction occurs due to the change in refractive index, thereby achieving frequency modulation of the optical signal from the optical waveguide microring resonator. Embedding the optical waveguide microring resonator within the piezoelectric material layer of the thin-film bulk acoustic wave resonator in Example 1 also optimizes the coupling effect between the two.

[0038] The following describes how to prepare the resonant device as described in Example 1.

[0039] Example 2:

[0040] Example 2 provides a method for fabricating a resonant device, see below. Figure 2 This includes the following steps:

[0041] Step 1: As Figure 2 As shown in (a), cavities are etched into the substrate 2-4 of the thin-film bulk acoustic resonator.

[0042] Step 2: As Figure 2 As shown in (b), a sacrificial layer is deposited to fill the cavity, and excess sacrificial layer is removed.

[0043] Step 3: As Figure 2 As shown in (c), the lower electrode layer 2-3 is deposited.

[0044] The process may include depositing a seed layer before depositing the lower electrode layer 2-3, and etching the lower electrode layer 2-3 into the desired shape after depositing the lower electrode layer 2-3.

[0045] Step 4: As Figure 2 As shown in (d), a piezoelectric material layer 2-2 is deposited above the lower electrode layer 2-3.

[0046] The piezoelectric material layer 2-2 is made of thin film materials with piezoelectric properties, such as aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, and lead zirconate titanate. For example, aluminum nitride thin films are often used as the piezoelectric material layer in thin-film bulk acoustic resonators. Aluminum nitride thin films are highly transparent materials that can be well coupled with optical microring resonators.

[0047] Step 5: As Figure 2As shown in (e), slots for embedding optical waveguide microring resonators are etched in the piezoelectric material layer 2-2.

[0048] Step 6: As shown in Figure 2(f), deposit the first material for forming the optical waveguide microring resonator.

[0049] The first material is a light guide material such as silicon or silicon dioxide, which has a large difference in refractive index from the medium in which it is located.

[0050] Step 7: See Figure 2 (g) and Figure 2 In step (h), the first material located above the piezoelectric material layer 2-2 is removed to form the target structure of the optical waveguide microring resonator.

[0051] The target structure of the optical waveguide microring resonator includes a linear waveguide 1-1 and a circular resonant microring 1-2. Figure 2 (g) in the diagram represents the side view of the structure obtained after step 7. Figure 2 (h) in the diagram represents the top view of the structure obtained after step 7.

[0052] Step 8: As Figure 2 As shown in (i), the upper electrode layer 2-1 is deposited.

[0053] In addition, see Figure 2 (j) and Figure 2 In step (k), after depositing the upper electrode layer 2-1, the process may further include etching the upper electrode layer 2-1 into the desired shape. The core working region of the upper electrode layer 2-1 and the core working region of the lower electrode layer 2-3 are both polygons, and both the core working regions of the upper electrode layer 2-1 and the lower electrode layer 2-3 cover the circular resonant microring 1-2 in a direction perpendicular to the electrode plane. Figure 2 In the diagram, (j) represents the side view corresponding to the obtained structure. Figure 2 In the diagram, (k) represents the top view corresponding to the obtained structure.

[0054] Step 9: Referring to (m) in 2, release the sacrificial layer to prepare the resonant device.

[0055] For example, the sacrificial layer can be released by introducing a corrosive gas.

[0056] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A resonant device, characterized in that, include: Optical waveguide microring resonators and thin-film bulk acoustic resonators; The thin-film bulk acoustic resonator includes an upper electrode layer, a piezoelectric material layer, and a lower electrode layer, wherein the piezoelectric material layer is located between the upper electrode layer and the lower electrode layer; The optical waveguide microring resonator is embedded in the piezoelectric material layer, and the optical waveguide microring resonator is coupled to the thin film bulk acoustic resonator. The optical waveguide microring resonator and the piezoelectric material layer have the same height and are seamlessly adjacent; The optical waveguide microring resonator includes a linear waveguide and a circular resonant microring; the optical signal enters from one end of the linear waveguide, generates a resonant signal through the circular resonant microring, and then exits from the other end of the linear waveguide.

2. The resonant device according to claim 1, characterized in that, The thin-film bulk acoustic resonator further includes a substrate, and a cavity is provided between the substrate and the lower electrode layer; the shape of the core working area of ​​the upper electrode layer and the shape of the core working area of ​​the lower electrode layer are the same polygon, and the core working areas of the upper electrode layer and the core working areas of the lower electrode layer are both covered by the circular resonant microring in the direction perpendicular to the electrode plane.

3. The resonant device according to claim 1, characterized in that, The piezoelectric material layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, and lead zirconate titanate; the optical waveguide microring resonator is made of silicon or silicon dioxide.

4. The resonant device according to claim 1, characterized in that, The piezoelectric material layer has etched slots, and the optical waveguide microring resonator is deposited in the slots.

5. A method for fabricating a resonant device, characterized in that, Includes the following steps: Step 1: Etch a cavity on the substrate of the thin-film bulk acoustic resonator; Step 2: Deposit a sacrificial layer to fill the cavity; Step 3: Deposit the lower electrode layer; Step 4: Deposit a piezoelectric material layer above the lower electrode layer; Step 5: Etch a slot in the piezoelectric material layer for embedding the optical waveguide microring resonator; Step 6: Deposit the first material used to form the optical waveguide microring resonator; Step 7: Remove the first material located above the piezoelectric material layer to form the target structure of the optical waveguide microring resonator; The target structure of the formed optical waveguide microring resonator includes a linear waveguide and a circular resonant microring. Step 8: Deposit the upper electrode layer; Step 9: Release the sacrificial layer to obtain the resonant device.

6. The method for preparing the resonant device according to claim 5, characterized in that, The first material is silicon or silicon dioxide.

7. The method for preparing the resonant device according to claim 5, characterized in that, The piezoelectric material layer is made of any one of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, or lead zirconate titanate.

8. The method for preparing the resonant device according to claim 6, characterized in that, In step 3, a seed layer is deposited before depositing the lower electrode layer, and the lower electrode layer is etched into the desired shape after depositing the lower electrode layer. In step 8, the upper electrode layer is etched into the desired shape after depositing the upper electrode layer. The shape of the core working area of ​​the upper electrode layer and the shape of the core working area of ​​the lower electrode layer are the same polygon, and the core working areas of the upper electrode layer and the core working areas of the lower electrode layer are both covered by the circular resonant microring in the direction perpendicular to the electrode plane. In step 9, the sacrificial layer is released by introducing a corrosive gas.

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