Acousto-optic modulator comprising a bragg grating

Abstract

The present disclosure provides a Bragg grating-containing acousto-optic modulator, which comprises an acoustic wave generating structure and a waveguide structure; an acousto-optic interaction section of the waveguide structure is a Bragg grating; the acoustic wave generating structure is used for receiving a radio frequency electrical signal and generating an acoustic wave based on the radio frequency electrical signal; the waveguide structure is used for receiving incident light and the acoustic wave, modulating the incident light in the Bragg grating, and outputting modulated light; wherein the acoustic wave is used for generating an acoustically-induced grating in the waveguide structure to change the refractive index of the Bragg grating, and a first light intensity corresponding to the incident light is less than a second light intensity corresponding to the modulated light. The present disclosure uses the Bragg grating in the acousto-optic interaction section of the acousto-optic modulator, utilizes the interaction between the acoustically-induced grating generated by the acoustic wave and the static Bragg grating, makes the light field in the region repeatedly reflect and interfere, increases the light intensity of the section and prolongs the residence time of the photons, and enhances the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

Description

Technical Field

[0001] This disclosure relates to the field of on-chip integrated optical technology, and more particularly to an acousto-optic modulator containing a Bragg grating. Background Technology

[0002] An acousto-optic modulator (AOM) is a multiphysics coupling device based on the acousto-optic effect, capable of precisely controlling the intensity, phase, frequency, or propagation direction of a laser. It plays an irreplaceable role in fields such as optical communication, laser processing, spectral analysis, quantum information processing, and optical sensing. Its core working principle utilizes a piezoelectric transducer to convert the input radio frequency electrical signal into a surface acoustic wave (SAW) based on the inverse piezoelectric effect of the piezoelectric material. This SAW propagates through the acousto-optic medium to a waveguide structure, causing a periodic change in the refractive index of the waveguide medium, forming an acousto-induced dynamic grating, thereby achieving intensity or phase modulation of the passing light wave. The piezoelectric transducer is typically an interdigital transducer (IDT).

[0003] Although acousto-optic technology has been developing for decades, traditional bulk acousto-optic modulators are usually based on bulk crystal materials such as tellurium oxide (TeO2). They are large in size, have high power consumption, and are difficult to be compatible with modern photonic integrated circuits (PICs), which severely limits their application in high-speed, high-density integrated optical systems.

[0004] To overcome these bottlenecks, integrated, on-chip acousto-optic modulators have become an important research direction. Among the many piezoelectric materials, gallium arsenide (GaAs), polycrystalline aluminum nitride, and lithium niobate on insulator (LNOI) are included. Thin-film lithium niobate (TFLN) platforms are favored due to their excellent piezoelectric and electro-optic effects and CMOS-compatible fabrication processes. However, the limited elastic-optic coefficient of pure lithium niobate material restricts further improvement in modulation efficiency. To address this, researchers have begun to explore heterogeneous integration schemes, combining chalcogenide glass (ChG) with TFLN to form a hybrid waveguide structure. This fully leverages the high efficiency of TFLN's electroacoustic conversion and the strong acousto-optic effect of ChG, significantly reducing the half-wave voltage-length product (V0). π L), to achieve higher modulation efficiency.

[0005] Despite significant progress in the development of on-chip acousto-optic modulators, the modulation efficiency of waveguide structures for optical signals remains low in practical applications. Summary of the Invention

[0006] The technical problem to be solved by this disclosure is to overcome the shortcomings of existing acousto-optic modulators, such as low modulation efficiency of optical signals, and to provide an acousto-optic modulator containing a Bragg grating.

[0007] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0008] This disclosure provides an acousto-optic modulator containing a Bragg grating, the acousto-optic modulator including an acoustic wave generation structure and a waveguide structure;

[0009] The acousto-optic section of the waveguide structure is a Bragg grating;

[0010] The sound wave generating structure is used to receive radio frequency electrical signals and generate sound waves based on the radio frequency electrical signals;

[0011] The waveguide structure is used to receive incident light and the sound wave, modulate the incident light in the Bragg grating, and output modulated light;

[0012] The acoustic wave is used to generate an acousto-optic grating in the waveguide structure to change the refractive index of the Bragg grating, and the first light intensity corresponding to the incident light is less than the second light intensity corresponding to the modulated light.

[0013] Optionally, the acoustic wave generating structure includes a piezoelectric layer and an interdigital transducer;

[0014] The interdigital transducer is disposed on the piezoelectric layer;

[0015] The interdigital transducer is used to receive the radio frequency electrical signal in order to generate the acoustic wave within the piezoelectric layer.

[0016] Optionally, the interdigital transducer is a split-finger interdigital transducer;

[0017] And / or,

[0018] The piezoelectric layer is made of lithium niobate;

[0019] And / or,

[0020] The thickness of the piezoelectric layer is 100nm-1000nm;

[0021] And / or,

[0022] The interdigital transducer adopts a dual-electrode interdigital transducer structure.

[0023] Optionally, the waveguide structure is a symmetrical Mach-Zehnder interferometer structure.

[0024] Optionally, one of the two connecting arms of the symmetrical Mach-Zehnder interferometer structure is provided with the Bragg grating, and the symmetrical Mach-Zehnder interferometer structure further includes a beam splitter and a beam combiner;

[0025] The beam splitter is used to receive the incident light and split the incident light into first and second beams.

[0026] The Bragg grating is used to modulate the first beam splitter to output the modulated light;

[0027] The beam combiner is used to combine the modulated light and the second split light to output combined light.

[0028] Optionally, both connecting arms of the symmetrical Mach-Zehnder interferometer structure are provided with the Bragg grating, and the symmetrical Mach-Zehnder interferometer structure further includes a beam splitter and a beam combiner;

[0029] The beam splitter is used to receive the incident light and split the incident light into first and second beams.

[0030] The Bragg gratings corresponding to the two connecting arms of the symmetrical Mach-Zehnder interferometer structure are used to modulate the first beam splitter and the second beam splitter, respectively, to output the first modulated light and the second modulated light.

[0031] The beam combiner is used to combine the first modulated light and the second modulated light to output a combined beam.

[0032] Optionally, the beam splitter is a multimode interference coupler;

[0033] And / or,

[0034] The beam combiner is a Y-type waveguide.

[0035] Optionally, the number of interdigitated fingers of the interdigitated transducer is odd.

[0036] And / or,

[0037] The interdigital transducer is disposed between the two connecting arms, and the center of the interdigital transducer is equidistant from the distance between the two connecting arms.

[0038] Optionally, the acoustic wave generating structure further includes several reflective gratings;

[0039] Several of the aforementioned reflective gratings are disposed on the piezoelectric layer and are symmetrically arranged with respect to the interdigital transducer;

[0040] The reflective grating is used to reflect the sound waves to enhance their amplitude.

[0041] Optionally, the acousto-optic modulator further includes a substrate layer disposed below the acoustic wave generating structure, wherein the substrate layer is made of silicon.

[0042] And / or,

[0043] The acousto-optic modulator also includes a silicon dioxide oxide layer disposed below the acoustic wave generating structure.

[0044] Optionally, the material of the reflective grating is chalcogenide glass;

[0045] And / or,

[0046] The electrode width of the reflective grating is 100nm-2000nm;

[0047] And / or,

[0048] The number of periods of the reflective grating is 5-30.

[0049] Optionally, the waveguide structure is made of a chalcogenide material;

[0050] And / or,

[0051] The width of the waveguide structure is 200nm-2000nm;

[0052] And / or,

[0053] The height of the waveguide structure is 300nm-1500nm;

[0054] And / or,

[0055] The waveguide structure operates at wavelengths of 1000nm-5000nm.

[0056] And / or,

[0057] The duty cycle of the Bragg grating is 0.2-0.8;

[0058] And / or,

[0059] The period of the Bragg grating is 200nm-1000nm;

[0060] And / or,

[0061] The etching depth of the Bragg grating is 100nm-900nm;

[0062] And / or,

[0063] The frequency of the sound waves is 500MHz-8GHz.

[0064] Optionally, the interdigital transducer includes a plurality of interdigital electrodes.

[0065] Optionally, the interdigitated electrodes are made of gold, aluminum, or copper;

[0066] And / or,

[0067] The thickness of the interdigitated electrodes is 80nm-500nm;

[0068] And / or,

[0069] The number of interdigitated electrodes is 10-100;

[0070] And / or,

[0071] The width of the interdigitated electrodes is 200nm-2000nm.

[0072] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this disclosure.

[0073] The positive and progressive effects of this disclosure are as follows:

[0074] This disclosure utilizes a Bragg grating in the acousto-optic section of an acousto-optic modulator. By using an acoustically induced grating generated by sound waves to interact with a static Bragg grating, the light field in this region undergoes repeated reflection and interference, increasing the light intensity of this section and prolonging the residence time of photons, thereby enhancing the acousto-optic coupling strength and the efficiency of acousto-optic modulation. Attached Figure Description

[0075] Figure 1 This is a schematic diagram of an acousto-optic modulator containing a Bragg grating according to Embodiment 1 of this disclosure;

[0076] Figure 2 This is a cross-sectional view of the acousto-optic modulator containing a Bragg grating according to Embodiment 2 of this disclosure;

[0077] Figure 3 This is a top view of the acousto-optic modulator containing a Bragg grating according to Embodiment 2 of this disclosure. Detailed Implementation

[0078] The present disclosure is further illustrated below by way of embodiments, but the present disclosure is not limited to the scope of the embodiments described herein.

[0079] The prefixes such as "first" and "second" used in this disclosure are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this disclosure does not constitute a limitation on the described objects. The description of the described objects is given in the context of the embodiments, and the use of such prefixes should not constitute unnecessary restrictions. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0080] Example 1

[0081] This embodiment provides an acousto-optic modulator containing a Bragg grating, such as Figure 1 As shown, the acousto-optic modulator includes an acoustic wave generation structure 1 and a waveguide structure 2;

[0082] The acousto-optic section of waveguide structure 2 is Bragg grating 211;

[0083] The sound wave generating structure 1 is used to receive radio frequency electrical signals and generate sound waves based on the radio frequency electrical signals;

[0084] Waveguide structure 2 is used to receive incident light and sound waves, modulate the incident light in Bragg grating 211, and output modulated light;

[0085] In this process, acoustic waves are used to generate an acoustic grating in the waveguide structure to change the refractive index of the Bragg grating 211, and the first light intensity corresponding to the incident light is less than the second light intensity corresponding to the modulated light.

[0086] Specifically, the waveguide structure can have one or more optical waveguides. If the waveguide structure has one optical waveguide, then a Bragg grating is placed on that single optical waveguide. If the waveguide structure has multiple optical waveguides, then a Bragg grating can be placed on at least one of the multiple optical waveguides.

[0087] The acousto-optic modulator's acousto-optic action section is a waveguide Bragg grating structure. The waveguide Bragg grating structure is a uniform periodic design, which is simple in structure, has low process requirements, is easier to design and manufacture, is easier to integrate, and makes information processing more stable and faster.

[0088] An external radio frequency electrical signal generates sound waves, namely surface acoustic waves, through a sound wave generating structure. The generated surface acoustic waves are transmitted to a waveguide structure, realizing the interaction between the sound field and the optical field.

[0089] In the acousto-optic interaction section, a waveguide Bragg grating structure is used in the waveguide to interact with a moving, periodic refractive index grating, i.e., an acousto-induced grating, which is formed by the periodic change in the local refractive index of the waveguide structure caused by the elasto-optic effect of surface acoustic waves.

[0090] A static WBG has been etched onto the waveguide structure. It is a fixed periodic structure that will form a photonic bandgap or stopband at a specific wavelength.

[0091] Acoustic gratings perturb the phase and coupling conditions of static Bragg gratings, effectively changing the effective refractive index or period of the static grating. This perturbation causes a slight shift in the stopband. This significantly alters the transmittance at the laser wavelength originally positioned at the stopband edge, resulting in strong modulation of the output light intensity. Simultaneously, it causes repeated reflections and interferences in this region, greatly enhancing the acousto-optic modulation efficiency, increasing the light intensity in this segment, and prolonging the photon residence time, thus strengthening the acousto-optic interaction.

[0092] Light of a specific wavelength, namely the Bragg center wavelength, is strongly reflected when it enters a Bragg grating, while light of other wavelengths can pass through the grating, thus forming a transmission valley. Surface acoustic waves alter the refractive index of a waveguide to form an acousto-optic grating, affecting the original grating structure and causing a frequency shift in the Bragg center wavelength, allowing light of that wavelength to pass through. Simultaneously, the change in refractive index caused by acoustic waves alters the propagation constant of light, thereby modulating the intensity of light transmission or reflection.

[0093] In this embodiment, by using a Bragg grating in the acousto-optic modulator's acousto-optic action section, the acoustic grating generated by the sound wave interacts with the static Bragg grating, causing the light field in this region to undergo repeated reflection and interference, increasing the light intensity of this section and prolonging the photon dwell time, thereby enhancing the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0094] Example 2

[0095] This embodiment provides an acousto-optic modulator containing a Bragg grating, such as Figure 2 and Figure 3 The figure shows a further improvement on Example 1.

[0096] In one feasible embodiment, the acoustic wave generating structure 1 includes a piezoelectric layer 11 and an interdigital transducer 12;

[0097] Interdigitated transducers 12 are disposed on piezoelectric layers 11;

[0098] Interdigital transducers 12 are used to receive radio frequency electrical signals to generate sound waves within the piezoelectric layer 11.

[0099] Specifically, the interdigital transducer can be placed on the inner or outer side of the waveguide structure.

[0100] like Figure 3 As shown, the interdigital transducer is located inside the waveguide structure and uses a dual-waveguide modulation mechanism to convert the input microwave signal into a surface acoustic wave signal, which then participates in the acousto-optic modulation process.

[0101] Interdigital transducers are placed on the outside of the waveguide structure and use a single waveguide modulation mechanism to convert the input microwave signal into a surface acoustic wave signal, which then participates in the acousto-optic modulation process.

[0102] In this scheme, a piezoelectric layer and interdigital transducers are used to convert radio frequency electrical signals into sound waves, ensuring the effectiveness and reliability of the sound wave generation structure.

[0103] In one feasible embodiment, the interdigital transducer 12 is a split-finger interdigital transducer.

[0104] Specifically, by utilizing the characteristics of harmonic suppression and actively reducing the number of finger pairs, the split-finger interdigital transducer can achieve a wider bandwidth than the single-electrode interdigital transducer.

[0105] In this scheme, the use of a split-finger interdigital transducer structure effectively suppresses harmonic response and allows the desired frequency characteristics to be achieved with a shorter transducer length, thereby directly expanding the bandwidth.

[0106] In one feasible embodiment, the piezoelectric layer 11 is made of lithium niobate (LiNbO3).

[0107] Specifically, the piezoelectric layer is a lithium niobate thin film. The tangential orientation of the lithium niobate thin film is YX, indicating that the normal direction of the device surface is along the Y-axis of the crystal, and the propagation direction of the surface acoustic wave is along the X-axis of the crystal. The Y-X shaped lithium niobate thin film has an outstanding high electromechanical coupling coefficient.

[0108] In this solution, a piezoelectric layer made of lithium niobate is used, which has a simple fabrication process. By making full use of the high piezoelectric properties of lithium niobate thin film material, a highly integrated and highly efficient acousto-optic modulator has been successfully realized, breaking through the technical bottleneck of improving acousto-optic modulation efficiency.

[0109] In one feasible approach, the thickness of the piezoelectric layer 11 is 100nm-1000nm.

[0110] Specifically, the thickness of the lithium niobate film is 100nm-1000nm.

[0111] In this solution, the modulation efficiency of the acousto-optic modulator is improved by optimizing the design of the piezoelectric layer thickness parameter.

[0112] In one feasible embodiment, the interdigital transducer 12 adopts a dual-electrode interdigital transducer structure.

[0113] In this scheme, by adopting an interdigital transducer with a dual-electrode structure, the modulation bandwidth is effectively improved, the intensity of acousto-optic interaction is enhanced, and thus the acousto-optic modulation efficiency is improved.

[0114] In one feasible scheme, waveguide structure 2 is a symmetrical Mach-Zehnder interferometer (MZI) structure.

[0115] In this scheme, a symmetrical Mach-Zehnder interferometer with a single or double arm structure is used to enhance the efficiency of acousto-optic modulation.

[0116] In one feasible embodiment, one of the two connecting arms of the symmetrical Mach-Zehnder interferometer structure 21 is provided with a Bragg grating 211, and the symmetrical Mach-Zehnder interferometer structure 21 also includes a beam splitter 212 and a beam combiner 213.

[0117] Beam splitter 212 is used to receive incident light and split the incident light into first and second beams.

[0118] Bragg grating 211 is used to modulate the first beam to output modulated light;

[0119] The beam combiner 213 is used to combine the modulated light and the second split light to output the combined light.

[0120] Specifically, a beam splitter can divide a light wave into two relatively uniform parts to adapt to the working principle of push-pull modulation in a Mach-Zehnder interferometer structure. A beam combiner can combine light waves with low loss. The waveguide Bragg grating structure, as a direct acousto-optic waveguide, utilizes the interaction between surface acoustic waves and the static Bragg grating and the characteristic of localizing the light field, thereby resulting in strong modulation of the output light intensity.

[0121] In this scheme, the single-arm modulation mechanism of the symmetrical Mach-Zehnder interferometer waveguide structure can be used to convert the change in refractive index into a change in phase. The Bragg grating waveguide structure is used to directly participate in the acousto-optic modulation process. By utilizing the interaction characteristics between surface acoustic waves and the Bragg static grating, the light field in this region is repeatedly reflected and interfered with, which increases the light intensity in this section and prolongs the residence time of photons, thereby enhancing the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0122] In one feasible embodiment, both connecting arms of the symmetrical Mach-Zehnder interferometer structure 21 are equipped with Bragg gratings 211, and the symmetrical Mach-Zehnder interferometer structure also includes a beam splitter 212 and a beam combiner 213.

[0123] Beam splitter 212 is used to receive incident light and split the incident light into first and second beams.

[0124] The Bragg gratings 211 corresponding to the two connecting arms of the symmetrical Mach-Zehnder interferometer structure are used to modulate the first beam splitter and the second beam splitter respectively, so as to output the first modulated light and the second modulated light.

[0125] The beam combiner 213 is used to combine the first modulated light and the second modulated light to output the combined light.

[0126] Specifically, the interaction between the Bragg grating and the acousto grating causes a strong modulation of the output light intensity. Combined with the MZI double-arm push-pull modulation mechanism, the first and second beams of the incident light are modulated in opposite ways. After beam combining, the output light is generated through interference superposition, resulting in a stronger modulation signal.

[0127] In this scheme, the change in refractive index can be converted into a change in phase through the double-arm modulation mechanism of the symmetrical Mach-Zehnder interferometer waveguide structure. The Bragg grating waveguide structure directly participates in the acousto-optic modulation process. By utilizing the interaction characteristics between surface acoustic waves and the Bragg static grating, the light field in this region is repeatedly reflected and interfered with, which increases the light intensity in this section and prolongs the residence time of photons, thereby enhancing the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0128] In one feasible embodiment, the beam splitter 212 is a multimode interference coupler (MMI).

[0129] Specifically, the multimode interference coupler is integrally formed with the waveguide structure, and the multimode interference coupler acts as a beam splitter. Its structural characteristics allow it to split the light wave into two relatively uniform parts, adapting to the working principle of push-pull modulation of the Mach-Zehnder interferometer structure, whether it is a double-arm or single-arm configuration.

[0130] In this scheme, a multimode interference coupler is used as a beam splitter, which can split the light wave into two parts relatively evenly to adapt to the working principle of push-pull modulation of the Mach-Zehnder interferometer structure.

[0131] In one feasible embodiment, the combiner 213 is a Y-shaped waveguide.

[0132] In this scheme, the Y-shaped waveguide, as a beam combiner, can perform optical wave beam combining with low loss.

[0133] In one feasible embodiment, the number of interdigitated exponents in the interdigitated transducer 12 is odd.

[0134] And / or,

[0135] The interdigitated transducer 12 is located between the two connecting arms, and the center of the interdigitated transducer 12 is equidistant from the distance between the two connecting arms.

[0136] Specifically, under a specific frequency drive, for an MZI-type waveguide structure, when the split-finger interdigitator is used in MZI dual-arm push-pull modulation, the interdigitation number of the split-finger interdigitator is an odd pair. Furthermore, when the split-finger interdigitator is placed between the two connecting arms of the MZI, the center of the split-finger interdigitator is equidistant from the distance between the two connecting arms, thereby producing opposite modulation effects or strains on the upper and lower connecting arms of the MZI. Finally, the output is generated through interference coupling via a beam combiner.

[0137] In this scheme, the split-finger interdigital transducer is located inside the MZI and adopts a dual-arm modulation mechanism to convert the input microwave signal into a surface acoustic wave signal, effectively suppressing the harmonic response and allowing the desired frequency characteristics to be achieved with a shorter transducer length, thereby expanding the bandwidth and participating in the acousto-optic modulation process.

[0138] In one feasible embodiment, the acoustic wave generating structure 1 further includes a plurality of reflective gratings 13;

[0139] Several reflective gratings 13 are disposed on the piezoelectric layer 11 and are symmetrically arranged about the interdigital transducer 12;

[0140] The reflector grating 13 is used to reflect sound waves to enhance their amplitude.

[0141] Specifically, the reflective grating is disposed on the lithium niobate film, and there are two sets of reflective gratings. The two sets of reflective gratings are symmetrically arranged about the interdigital transducer and are located on both sides of the interdigital transducer.

[0142] In this scheme, sound waves are reflected by setting a reflective grating. The reflected sound waves and the excited sound waves coherently and constructively interact, which greatly enhances the amplitude of the sound waves and significantly strengthens the intensity of the sound-light interaction.

[0143] In one feasible embodiment, the acousto-optic modulator further includes a substrate layer 3 disposed below the acoustic wave generating structure 1, the substrate layer 3 being made of silicon (Si); and / or, the acousto-optic modulator further includes a silicon dioxide (SiO2) oxide layer 4 disposed below the acoustic wave generating structure 1.

[0144] Specifically, the acousto-optic modulator comprises, from bottom to top, a silicon substrate, a silicon dioxide oxide layer, and a lithium niobate-chalcogenide glass heterostructure. The lithium niobate-chalcogenide glass heterostructure includes a lithium niobate thin film and a chalcogenide optical waveguide heterogeneously integrated on the lithium niobate thin film. An interdigitated transducer and a reflective grating are also disposed on the lithium niobate thin film. The substrate includes a silicon substrate and a silicon dioxide layer disposed on the silicon substrate, with the lithium niobate-chalcogenide glass heterostructure disposed on the silicon dioxide layer. The lithium niobate-chalcogenide glass heterostructure is in a non-suspended state relative to the substrate; that is, the lithium niobate-chalcogenide glass heterostructure is directly attached to the substrate.

[0145] In acousto-optic modulators, silicon dioxide and silicon play key roles in providing support, thermal insulation, optical isolation, and acoustic isolation.

[0146] In this scheme, a complete acousto-optic modulator is formed by setting a silicon substrate layer and a silicon dioxide oxide layer, which ensures the reliability of the device.

[0147] In one feasible embodiment, the reflector grating 13 is made of chalcogenide glass.

[0148] In this scheme, chalcogenide glass is used as the material for the acoustic reflection grating. The high reflectivity and strong sound field confinement of chalcogenide glass are naturally compatible with the hybrid waveguide, achieving synergistic enhancement and improving the utilization rate of sound wave energy.

[0149] In one feasible embodiment, the electrode width of the reflective grating 13 is 100 nm to 2000 nm, and / or the number of periods of the reflective grating 13 is 5 to 30.

[0150] In this scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the design of parameters such as the electrode width and the number of cycles of the reflective grating.

[0151] In one feasible scheme, the waveguide structure 2 is made of a chalcogenide material.

[0152] Specifically, chalcogenide materials are chalcogenide glasses (Ge). 28 Sb 12 Se 60 ).

[0153] This scheme employs a waveguide structure made of chalcogenide materials. The hybrid integration structure of lithium niobate thin film and chalcogenide materials effectively confines most of the light energy within the ChG (chalcogenide glass) waveguide, thereby fully utilizing the dominant photoelastic effect and significantly improving modulation efficiency. This optimization not only fully utilizes the excellent optical properties of chalcogenide materials but also provides greater flexibility and performance potential for optical device design, thus exhibiting more significant advantages in high-speed optical modulation applications. The fabrication process is simple, successfully realizing a highly integrated and highly efficient chalcogenide acousto-optic modulator, breaking through the technical bottleneck of improving acousto-optic modulation efficiency. The entire acousto-optic modulator device is hybrid-integrated on lithium niobate and chalcogenide thin film platforms, demonstrating good process compatibility, excellent stability, and easy scalability. Simultaneously, this design combines simple fabrication, high robustness, and large-scale integration capabilities, opening up new ideas and solutions for the practical application of thin-film acousto-optic modulators.

[0154] In one feasible embodiment, the width of the waveguide structure is 200nm-2000nm, and / or the height of the waveguide structure 2 is 300nm-1500nm, and / or the operating wavelength of the waveguide structure 2 is 1000nm-5000nm.

[0155] In this scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the design of parameters such as the width, height and operating wavelength of the waveguide structure.

[0156] In one feasible embodiment, the duty cycle of the Bragg grating 211 is 0.2-0.8, and / or the period of the Bragg grating 211 is 200nm-1000nm, and / or the etching depth of the Bragg grating 211 is 100nm-900nm.

[0157] In this scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the parameters such as the duty cycle, period, and etching depth of the Bragg grating.

[0158] In one feasible approach, the frequency of the sound waves is 500MHz-8GHz.

[0159] Specifically, the split-finger interdigital transducer can achieve the excitation of Rayleigh surface acoustic waves in the 500MHz-8GHz range.

[0160] In this scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the design of the frequency parameter of the surface acoustic wave.

[0161] In one feasible embodiment, the interdigital transducer 12 includes a plurality of interdigital electrodes, and / or the material of the interdigital electrodes of the interdigital transducer 12 is gold, aluminum or copper, and / or the thickness of the interdigital electrodes is 80nm-500nm, and / or the number of interdigital electrodes is 10-100, and / or the width of the interdigital electrodes is 200nm-2000nm.

[0162] In this scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the design of parameters such as the material, thickness, logarithm, and width of the interdigital electrodes of the interdigital transducer.

[0163] The working principle of the acousto-optic modulator containing a Bragg grating in this embodiment is explained below with specific examples:

[0164] Based on the inverse piezoelectric coupling effect of lithium niobate thin films, the input microwave signal is converted into a surface acoustic wave (SAW) signal from the lithium niobate thin film via a split-fin interdigital transducer. This causes a mechanical strain field distribution in the lithium niobate thin film. The mechanical acoustic waves generated on the surface of the lithium niobate thin film further act on a chalcogenide optical waveguide. This process, based on the optomechanical coupling effect, changes the optical refractive index of the chalcogenide optical waveguide. Furthermore, through the double-arm modulation mechanism of a symmetrical Mach-Zehnder interferometer waveguide structure, stresses in opposite directions are generated on the two sides of the waveguide, changing the refractive index of the chalcogenide optical waveguide and converting the refractive index change into a phase change. The optomechanical coupling effect includes the moving boundary effect, the elasto-optic effect, and the electro-optic effect.

[0165] Simultaneously, a waveguide Bragg grating (WBG) structure is used to directly participate in the acousto-optic modulation process. Utilizing the interaction between acoustic waves and the static Bragg grating, the resulting acousto-induced grating interacts with the static WBG. The acousto-induced grating perturbs the phase and coupling conditions of the static grating, effectively changing its effective refractive index or period. This perturbation causes a slight shift in the stopband. This significantly changes the transmittance at the laser wavelength originally positioned at the stopband edge, resulting in strong modulation of the output light intensity. Furthermore, it allows the light wave to repeatedly reflect and diffract in this grating region, increasing the light intensity in that segment and prolonging the photon residence time. This transforms the weak acousto-optic effect into efficient intensity modulation, enhancing the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0166] Simultaneously, the use of a split-finger interdigital transducer structure effectively suppresses harmonic response, thereby expanding the operating bandwidth. Furthermore, the use of an acoustic reflection grating made of chalcogenide materials leverages the high reflectivity and strong acoustic field confinement of chalcogenide glass, naturally compatible with the hybrid waveguide, to achieve synergistic enhancement and improve the utilization rate of acoustic energy. This results in a novel acousto-optic modulator with high modulation efficiency, large bandwidth, stable operation, and easier integration and manufacturing.

[0167] The acousto-optic modulator with a Bragg grating provided in this embodiment ingeniously utilizes the interaction between sound waves and a static waveguide grating to transform weak acousto-optic effects into efficient intensity modulation. The use of a split-finger interdigital transducer significantly improves the operating bandwidth. Simultaneously, an acoustic reflection grating made of chalcogenide glass is used to confine the sound field intensity. It achieves an excellent balance between modulation efficiency, coupling strength, bandwidth, stability, and complexity, exhibiting high modulation efficiency, strong coupling strength, large bandwidth, high speed, stable operation, and easier integration and manufacturing. This makes it a very promising on-chip integrated acousto-optic modulation scheme.

[0168] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. A Bragg grating containing acousto-optic modulator, characterized by, The acousto-optic modulator includes an acoustic wave generation structure and a waveguide structure; The acousto-optic section of the waveguide structure is a Bragg grating; The sound wave generating structure is used to receive radio frequency electrical signals and generate sound waves based on the radio frequency electrical signals; The waveguide structure is used to receive incident light and the sound wave, modulate the incident light in the Bragg grating, and output modulated light; The acoustic wave is used to generate an acousto-optic grating in the waveguide structure to change the refractive index of the Bragg grating, and the first light intensity corresponding to the incident light is less than the second light intensity corresponding to the modulated light. The waveguide structure is a symmetrical Mach-Zehnder interferometer structure; Both connecting arms of the symmetrical Mach-Zehnder interferometer structure are equipped with the Bragg grating, and the symmetrical Mach-Zehnder interferometer structure also includes a beam splitter and a beam combiner; The beam splitter is used to receive the incident light and split the incident light into first and second beams. The Bragg gratings corresponding to the two connecting arms of the symmetrical Mach-Zehnder interferometer structure are used to modulate the first beam splitter and the second beam splitter, respectively, to output the first modulated light and the second modulated light. The beam combiner is used to combine the first modulated light and the second modulated light to output combined light; The acoustic wave generating structure includes a piezoelectric layer and an interdigital transducer; The interdigital transducer is disposed on the piezoelectric layer; The interdigital transducer is used to receive the radio frequency electrical signal in order to generate the acoustic wave within the piezoelectric layer; The interdigital transducer is a split-fin interdigital transducer; The interdigitation index of the interdigital transducer is an odd number of pairs; The Bragg grating forms a photonic bandgap or stopband at a specific wavelength. The acousto grating is used to perturb the phase and coupling conditions of the Bragg grating, which is equivalent to dynamically changing the effective refractive index of the Bragg grating, causing a slight shift in the stopband, and causing a significant change in the transmittance at the laser wavelength at the edge of the stopband, thereby strongly modulating the output light intensity. Furthermore, within the region of the Bragg grating, the light field undergoes repeated reflection and interference to increase the light intensity and prolong the residence time of photons.

2. The Bragg grating containing acousto-optic modulator of claim 1, wherein, The piezoelectric layer is made of lithium niobate; And / or, The thickness of the piezoelectric layer is 100nm-1000nm; And / or, The interdigital transducer adopts a dual-electrode interdigital transducer structure.

3. The acousto-optic modulator containing a Bragg grating as described in claim 2, characterized in that, The beam splitter is a multimode interference coupler; And / or, The beam combiner is a Y-type waveguide.

4. The acousto-optic modulator containing a Bragg grating as described in claim 2, characterized in that, The interdigital transducer is disposed between the two connecting arms, and the center of the interdigital transducer is equidistant from the distance between the two connecting arms.

5. The acousto-optic modulator containing a Bragg grating as described in claim 1, characterized in that, The acoustic wave generating structure also includes several reflective gratings; Several of the aforementioned reflective gratings are disposed on the piezoelectric layer and are symmetrically arranged with respect to the interdigital transducer; The reflective grating is used to reflect the sound waves to enhance their amplitude.

6. The acousto-optic modulator containing a Bragg grating as described in any one of claims 1-2, characterized in that, The acousto-optic modulator further includes a substrate layer disposed below the acoustic wave generating structure, the substrate layer being made of silicon; And / or, The acousto-optic modulator also includes a silicon dioxide oxide layer disposed below the acoustic wave generating structure.

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