Acousto-optic modulator comprising Bragg grating

Abstract

The invention provides an acousto-optic modulator comprising a Bragg grating. The acousto-optic modulator comprises a sound wave generation structure and a waveguide structure, the acousto-optic action section of the waveguide structure is a Bragg grating; the sound wave generation structure is used for receiving the radio-frequency electric signals and generating sound waves based on the radio-frequency electric signals; the waveguide structure is used for receiving incident light and sound waves, modulating the incident light in the Bragg grating and outputting modulated light; wherein the sound wave is used for generating a sound-induced grating in the waveguide structure so as to change the refractive index of the Bragg grating, and the first light intensity corresponding to the incident light is smaller than the second light intensity corresponding to the modulated light. According to the invention, the Bragg grating is used in the acousto-optic action section of the acousto-optic modulator, and the acoustic grating generated by sound waves interacts with the static Bragg grating, so that the light field in the area is repeatedly reflected and interfered, the light intensity of the section is increased, and the retention time of photons is prolonged. And the acousto-optic coupling strength and the acousto-optic modulation efficiency are enhanced.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of integrated optical technology on chip, and in particular to an acousto-optic modulator containing a Bragg grating. BACKGROUND

[0002] An acousto-optic modulator (AOM) is a multi-physical field coupling device based on the acousto-optic effect, which can accurately regulate the intensity, phase, frequency or propagation direction of laser. It plays an irreplaceable role in the fields of optical communication, laser processing, spectral analysis, quantum information processing and optical sensing. Its core working principle is to use a piezoelectric transducer to convert the input radio frequency electrical signal into a surface acoustic wave (SAW) according to the inverse piezoelectric effect of piezoelectric materials. The acoustic wave propagates in the waveguide structure of the acousto-optic medium, causing a periodic change in the refractive index of the waveguide structure medium, forming an acoustic dynamic grating, thereby achieving intensity or phase modulation of the passing light wave. The piezoelectric transducer is usually an interdigital transducer (IDT).

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

[0004] To overcome these bottlenecks, integrated and 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) platform is favored due to its excellent piezoelectric effect, electro-optic effect, and CMOS-compatible fabrication process. However, the photoelastic coefficient of pure lithium niobate material is limited, which restricts the further improvement of modulation efficiency. Therefore, researchers have begun to explore hetero-integration solutions, combining chalcogenide glass (ChG) with high photoelastic coefficient and TFLN to form a hybrid waveguide structure, fully utilizing the high-efficiency electro-acoustic conversion capability of TFLN and the strong acousto-optic effect of ChG, significantly reducing the half-wave voltage-length product (V π L), and achieving higher modulation efficiency.

[0005] Although significant progress has been made in the development of on-chip acousto-optic modulators, the modulation efficiency of the waveguide structure on the optical signal is still low in practical applications. SUMMARY

[0006] The technical problem to be solved by the present disclosure is to overcome the low modulation efficiency of the acousto-optic modulator on the optical signal in the prior art, and to provide an acousto-optic modulator containing a Bragg grating.

[0007] The present disclosure solves the above technical problems through the following technical solutions:

[0008] The present disclosure provides an acoustic-optical modulator containing a Bragg grating, which comprises an acoustic wave generating structure and a waveguide structure.

[0009] The acoustic-optical interaction section of the waveguide structure is a Bragg grating.

[0010] The acoustic wave generating structure is used to receive a radio frequency electrical signal and generate an acoustic wave based on the radio frequency electrical signal.

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

[0012] The acoustic wave is used to generate an acoustic-induced 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 comprises a piezoelectric layer and an interdigital transducer.

[0014] The interdigital transducer is arranged on the piezoelectric layer.

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

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

[0017] And / or,

[0018] The material of the piezoelectric layer is lithium niobate.

[0019] And / or,

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

[0021] And / or,

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

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

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

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

[0026] The Bragg grating is configured to modulate the first split light to output the modulated light.

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

[0028] Optionally, the two connecting arms of the symmetric Mach-Zehnder interferometer structure are both provided with the Bragg grating, and the symmetric Mach-Zehnder interferometer structure further comprises a beam splitter and a beam combiner.

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

[0030] The Bragg grating corresponding to the two connecting arms of the symmetric Mach-Zehnder interferometer structure is configured to modulate the first split light and the second split light respectively to output a first modulated light and a second modulated light.

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

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

[0033] And / or,

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

[0035] Optionally, the number of prongs of the interdigital transducer is an odd number.

[0036] And / or,

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

[0038] Optionally, the acoustic wave generating structure further comprises a plurality of reflection gratings.

[0039] The plurality of reflection gratings are arranged on the piezoelectric layer and symmetrically arranged with respect to the interdigital transducer.

[0040] The reflection gratings are configured to reflect the acoustic wave to enhance the amplitude of the acoustic wave.

[0041] Optionally, the acousto-optic modulator further comprises a substrate layer arranged below the acoustic wave generating structure, and the material of the substrate layer is silicon.

[0042] And / or,

[0043] The acousto-optic modulator further comprises a silicon oxide layer arranged 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 100-2000 nm.

[0047] and / or,

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

[0049] Optionally, the material of the waveguide structure is chalcogenide material.

[0050] and / or,

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

[0052] and / or,

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

[0054] and / or,

[0055] The operating wavelength of the waveguide structure is 1000-5000 nm.

[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 200-1000 nm.

[0060] and / or,

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

[0062] and / or,

[0063] The frequency of the acoustic wave is 500 MHz-8 GHz.

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

[0065] Optionally, the material of the interdigital electrodes is gold, aluminum or copper.

[0066] and / or,

[0067] The thickness of the interdigital electrode is 80-500nm;

[0068] and / or,

[0069] The logarithm of the interdigital electrode is 10-100;

[0070] and / or,

[0071] The width of the interdigital electrode is 200-2000nm.

[0072] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, i.e. to obtain each preferred example of the present disclosure.

[0073] The positive progress effect of the present disclosure is that:

[0074] The present disclosure uses Bragg grating in the acousto-optic interaction section of the acousto-optic modulator, utilizes the acousto-optic grating generated by the acoustic wave to interact with the static Bragg grating, makes the light field in this region repeatedly reflect and interfere, increases the light intensity of this section and prolongs the residence time of the photon, enhances the acousto-optic coupling strength and the efficiency of acousto-optic modulation. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 The figure is a schematic diagram of the Bragg grating-containing acousto-optic modulator of Example 1 of the present disclosure;

[0076] Figure 2 The figure is a cross-sectional view of the Bragg grating-containing acousto-optic modulator of Example 2 of the present disclosure;

[0077] Figure 3 The figure is a top view of the Bragg grating-containing acousto-optic modulator of Example 2 of the present disclosure. DETAILED DESCRIPTION

[0078] The present disclosure will be further described below by way of examples, but the present disclosure is not limited in the scope of the examples.

[0079] In the examples of the present disclosure, the prefix words such as "first", "second" are used only to distinguish different description objects, and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of ordinal words such as ordinal words in the examples of the present disclosure does not limit the described objects, and the description of the described objects should be seen in the context of the examples, and should not be construed as redundant limitation because of the use of such prefix words. In addition, in the description of the examples, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0080] Example 1

[0081] The embodiment provides an acoustic-optical modulator containing a Bragg grating, as shown in the figure. Figure 1 The acoustic-optical modulator comprises an acoustic wave generating structure 1 and a waveguide structure 2.

[0082] An acoustic-optical interaction section of the waveguide structure 2 is a Bragg grating 211.

[0083] The acoustic wave generating structure 1 is used for receiving a radio frequency electric signal and generating an acoustic wave based on the radio frequency electric signal.

[0084] The waveguide structure 2 is used for receiving incident light and the acoustic wave, modulating the incident light in the Bragg grating 211, and outputting modulated light.

[0085] The acoustic wave is used for generating an acousto-optic grating in the waveguide structure to change the refractive index of the Bragg grating 211, and a first light intensity corresponding to the incident light is less than a second light intensity corresponding to the modulated light.

[0086] Specifically, the waveguide structure can have one or more light waveguides. If the waveguide structure has one light waveguide, the Bragg grating is arranged on the one light waveguide. If the waveguide structure has more than one light waveguide, the Bragg grating can be arranged on at least one of the more than one light waveguides.

[0087] The acoustic-optical interaction section of the acoustic-optical modulator is a waveguide Bragg grating structure, the waveguide Bragg grating structure is a uniform period design, the structure is simple, the process requirement is low, the design and manufacturing difficulty is low, the integration design is easier, and the information processing is more stable and fast.

[0088] An external radio frequency electric signal generates an acoustic wave, i.e., a surface acoustic wave, through the acoustic wave generating structure, the generated surface acoustic wave is transmitted to the waveguide structure, and the interaction between the acoustic field and the optical field is realized.

[0089] In the waveguide of the acoustic-optical interaction section, the waveguide Bragg grating structure interacts with a moving and periodic refractive index grating, i.e., an acousto-optic grating, which is formed by the photoelastic effect of the surface acoustic wave and causes the local refractive index of the waveguide structure to change periodically.

[0090] A static WBG has been etched on the waveguide structure, and the static WBG itself is a fixed periodic structure, which forms a photonic band gap or a stop band at a specific wavelength.

[0091] The acousto-optic grating disturbs the phase and coupling condition of the static Bragg grating, which is equivalent to dynamically changing the effective refractive index or period of the static grating. The disturbance of the acousto-optic grating causes a slight shift of the stop band. This causes the transmittance at the originally set laser wavelength on the edge of the stop band to change significantly, resulting in strong modulation of the output light intensity, while the light field in this region repeatedly reflects and interferes, greatly enhancing the acousto-optic modulation efficiency, increasing the light intensity in this section and prolonging the residence time of the photons, enhancing the strength of the acousto-optic interaction.

[0092] The light wave of a specific wavelength, i.e. the Bragg center wavelength, is strongly reflected by the Bragg grating, while light of other wavebands can pass through the grating, thereby forming a transmission valley. The surface acoustic wave changes the refractive index of the waveguide to form an acousto-optic grating, which affects the original grating structure, causing the Bragg center wavelength to shift, causing the light of this wavelength to transmit out. The refractive index change caused by the acoustic wave changes the light propagation constant, thereby modulating the transmission or reflection intensity of the light.

[0093] In this embodiment, by using a Bragg grating in the acousto-optic interaction section of the acousto-optic modulator, the acousto-optic grating generated by the acoustic wave interacts with the static Bragg grating, causing the light field in this region to repeatedly reflect and interfere, increasing the light intensity in this section and prolonging the residence time of the photons, enhancing the strength of the acousto-optic coupling and the efficiency of the acousto-optic modulation.

[0094] Embodiment 2

[0095] This embodiment provides an acousto-optic modulator containing a Bragg grating, as shown in Figure 2 and Figure 3 which is a further improvement of embodiment 1.

[0096] In an implementable scheme, the acoustic wave generating structure 1 includes a piezoelectric layer 11 and an interdigital transducer 12.

[0097] The interdigital transducer 12 is arranged on the piezoelectric layer 11.

[0098] The interdigital transducer 12 is used to receive a radio frequency electrical signal to generate an acoustic wave in the piezoelectric layer 11.

[0099] Specifically, the interdigital transducer can be arranged on the inside or the outside of the waveguide structure.

[0100] As shown in Figure 3 , the interdigital transducer is arranged on the inside of the waveguide structure, and adopts a double waveguide modulation mechanism to convert the input microwave signal into a surface acoustic wave signal to participate in the acousto-optic modulation process.

[0101] The interdigital transducer is arranged on the outside of the waveguide structure, and adopts a single waveguide modulation mechanism to convert the input microwave signal into a surface acoustic wave signal to participate in the acousto-optic modulation process.

[0102] In the scheme, the piezoelectric layer and the interdigital transducer are used to convert the radio frequency electrical signal into acoustic wave, ensuring the effectiveness and reliability of the acoustic wave generation structure.

[0103] In an implementable scheme, the interdigital transducer 12 is a split-finger interdigital transducer.

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

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

[0106] In an implementable scheme, the material of the piezoelectric layer 11 is lithium niobate (LiNbO3).

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

[0108] In the scheme, by using the piezoelectric layer of lithium niobate material, the preparation process is simple, and the high piezoelectric performance of the lithium niobate thin film material is fully utilized, successfully realizing a high-integration and high-modulation-efficiency acousto-optic modulator, and breaking through the technical bottleneck of improving the acousto-optic modulation efficiency.

[0109] In an implementable scheme, the thickness of the piezoelectric layer 11 is 100nm-1000nm.

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

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

[0112] In an implementable scheme, the interdigital transducer 12 adopts a double-electrode interdigital transducer structure.

[0113] In the scheme, by using the interdigital transducer with a double-electrode structure, the modulation bandwidth is effectively improved, the acousto-optic interaction strength is enhanced, and the acousto-optic modulation efficiency is improved.

[0114] In an implementable scheme, the waveguide structure 2 is a symmetric Mach-Zehnder interferometer (MZI) structure.

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

[0116] In an implementable solution, one of the two connecting arms of the symmetric Mach-Zehnder interferometer structure 21 is provided with a Bragg grating 211, and the symmetric Mach-Zehnder interferometer structure 21 further comprises a beam splitter 212 and a beam combiner 213.

[0117] The beam splitter 212 is configured to receive incident light and split the incident light to obtain first split light and second split light.

[0118] The Bragg grating 211 is configured to modulate the first split light to output modulated light.

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

[0120] Specifically, the beam splitter can split the light waves into two parts to adapt to the working principle of the double-arm push-pull modulation of the Mach-Zehnder interferometer structure. The beam combiner can combine the light waves with low loss. The waveguide Bragg grating structure is a direct acousto-optic interaction section waveguide, which utilizes the interaction between the surface acoustic wave and the Bragg static grating and the characteristics of localizing the optical field, thereby causing strong modulation of the output light intensity.

[0121] In the solution, the change of the refractive index is converted into the change of the phase through the single-arm modulation mechanism of the symmetric Mach-Zehnder interferometer waveguide structure, the Bragg grating waveguide structure is directly involved in the process of acousto-optic modulation, the characteristics of the interaction between the surface acoustic wave and the Bragg static grating are utilized to make the light field in the region repeatedly reflect and interfere, increase the light intensity of the section and prolong the residence time of the photons, and enhance the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0122] In an implementable solution, one of the two connecting arms of the symmetric Mach-Zehnder interferometer structure 21 is provided with a Bragg grating 211, and the symmetric Mach-Zehnder interferometer structure 21 further comprises a beam splitter 212 and a beam combiner 213.

[0123] The beam splitter 212 is configured to receive incident light and split the incident light to obtain first split light and second split light.

[0124] The Bragg gratings 211 corresponding to the two connecting arms of the symmetric Mach-Zehnder interferometer structure are configured to modulate the first split light and the second split light, respectively, to output first modulated light and second modulated light.

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

[0126] Specifically, through the interaction of the Bragg grating and the acousto-optic grating, the output light intensity is strongly modulated, and the first and second split lights corresponding to the incident light are subjected to opposite modulation effects and are combined to output, and a stronger modulation signal is obtained through interference superposition.

[0127] In the scheme, the change of the refractive index is converted into the change of the phase through the double-arm modulation mechanism of the symmetric Mach-Zehnder interferometer waveguide structure, the Bragg grating waveguide structure is directly involved in the process of acousto-optic modulation, the characteristics of the interaction between the surface acoustic wave and the Bragg static grating are used to make the light field in the region repeatedly reflect and interfere, increase the light intensity in the section and prolong the residence time of the photons, and enhance the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0128] In an implementable scheme, 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 functions as a beam splitter. Its structural characteristics enable it to divide the light wave into two parts to adapt to the working principle of the double-arm or single-arm push-pull modulation of the Mach-Zehnder interferometer structure.

[0130] In the scheme, the multimode interference coupler is used as the beam splitter, which can divide the light wave into two parts to adapt to the working principle of the double-arm or single-arm push-pull modulation of the Mach-Zehnder interferometer structure.

[0131] In an implementable scheme, the beam combiner 213 is a Y-shaped waveguide.

[0132] In the scheme, the Y-shaped waveguide as the beam combiner can combine the light waves with low loss.

[0133] In an implementable scheme, the number of prongs of the interdigital transducer 12 is an odd number.

[0134] And / or,

[0135] The interdigital transducer 12 is arranged between the two connecting arms, and the center of the interdigital transducer 12 is equidistant from the two connecting arms.

[0136] Specifically, the split-finger interdigital transducer, when driven at a specific frequency, has an odd number of split-finger interdigital transducer prongs for the MZI type waveguide structure, and when the split-finger interdigital transducer is used for MZI double-arm push-pull modulation, the number of split-finger interdigital transducer prongs is an odd number, and when the split-finger interdigital transducer is placed between the two connecting arms of the MZI, the center of the split-finger interdigital transducer is equidistant from the two connecting arms, to produce opposite modulation effects or strains on the upper and lower connecting arms of the MZI, and finally output through the interference coupling of the beam combiner.

[0137] In the scheme, the split-finger interdigital transducer is arranged inside the MZI, and the input microwave signal is converted into a surface acoustic wave signal by using a double-arm modulation mechanism, thereby effectively suppressing the harmonic response and allowing the required frequency characteristics to be achieved in a shorter transducer length, thus expanding the bandwidth and participating in the acousto-optic modulation process.

[0138] In an implementable scheme, the acoustic wave generating structure 1 further comprises a plurality of reflection gratings 13;

[0139] The plurality of reflection gratings 13 are arranged on the piezoelectric layer 11 and are symmetrically arranged with respect to the interdigital transducer 12.

[0140] The reflection gratings 13 are used to reflect the acoustic waves to enhance the amplitude of the acoustic waves.

[0141] Specifically, the reflection gratings are arranged on the lithium niobate thin film and are provided in two groups, and the two groups of reflection gratings are symmetrically arranged with respect to the interdigital transducer and are located on the two sides of the interdigital transducer.

[0142] In the scheme, the reflection gratings are arranged to reflect the acoustic waves, and the reflected acoustic waves are coherent with the excited acoustic waves, thereby greatly enhancing the amplitude of the acoustic waves and significantly enhancing the intensity of the acousto-optic interaction.

[0143] In an implementable scheme, the acousto-optic modulator further comprises a substrate layer 3 arranged below the acoustic wave generating structure 1, and the material of the substrate layer 3 is silicon (Si); and / or, the acousto-optic modulator further comprises a silicon dioxide (SiO2) oxide layer 4 arranged below the acoustic wave generating structure 1.

[0144] Specifically, the acousto-optic modulator comprises a silicon substrate layer, a silicon dioxide oxide layer, and a lithium niobate-chalcogenide glass heterostructure layer arranged in sequence from bottom to top, wherein the lithium niobate-chalcogenide glass heterostructure layer comprises a lithium niobate thin film and a chalcogenide optical waveguide heterogeneously integrated on the lithium niobate thin film, and the interdigital transducer and the reflection grating are further arranged on the lithium niobate thin film. The substrate comprises a silicon substrate and a silicon dioxide layer arranged on the silicon substrate, and the lithium niobate-chalcogenide glass heterostructure layer is arranged on the silicon dioxide layer. The lithium niobate-chalcogenide glass heterostructure layer is in a non-suspended state with respect to the substrate, i.e., the lithium niobate-chalcogenide glass heterostructure layer is directly attached to the substrate.

[0145] In the acousto-optic modulator, silicon dioxide and silicon mainly play a key role in supporting, heat insulation, optical isolation, and acoustic isolation.

[0146] In the scheme, by arranging the silicon substrate layer and the silicon dioxide oxide layer, a complete acousto-optic modulator is formed, thereby ensuring the reliability of the device.

[0147] In an implementable scheme, the material of the reflection grating 13 is chalcogenide glass.

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

[0149] In an implementable scheme, the electrode width of the reflection grating 13 is 100 nm-2000 nm, and / or the period number of the reflection grating 13 is 5-30.

[0150] In the scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the electrode width and period number of the reflection grating.

[0151] In an implementable scheme, the material of the waveguide structure 2 is a chalcogenide material.

[0152] Specifically, the chalcogenide material is chalcogenide glass (Ge 28 Sb 12 Se 60 ).

[0153] In the scheme, the waveguide structure of the chalcogenide material, and the mixed integration structure of the lithium niobate thin film and the chalcogenide material make most of the light energy be effectively limited in the ChG (chalcogenide glass) waveguide, so as to fully utilize the dominant photoelastic effect and significantly improve the modulation efficiency. This optimization not only fully utilizes the excellent optical performance of the chalcogenide material, but also provides higher flexibility and stronger performance potential for optical device design, thereby showing more obvious advantages in high-speed optical modulation applications. The preparation process is simple, and the chalcogenide acousto-optic modulator with high integration and high modulation efficiency is successfully realized, breaking through the technical bottleneck of improving the acousto-optic modulation efficiency. The entire acousto-optic modulator device is realized by mixed integration on the lithium niobate thin film and the chalcogenide thin film platform, showing good process compatibility, excellent stability, and the advantages of easy large-scale expansion. At the same time, the design has the advantages of simple process, high robustness and large-scale integration capability, which opens up a new way of thinking and solution for the practicalization of thin film acousto-optic modulators.

[0154] In an implementable scheme, the width of the waveguide structure is 200 nm-2000 nm, and / or the height of the waveguide structure 2 is 300 nm-1500 nm, and / or the working wavelength of the waveguide structure 2 is 1000 nm-5000 nm.

[0155] In the scheme, the modulation efficiency of the acousto-optic modulator is improved by optimizing the width, height and working wavelength of the waveguide structure.

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

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

[0158] In an implementable scheme, the frequency of the acoustic wave is 500MHz-8GHz.

[0159] Specifically, the split interdigital transducer can realize the excitation of 500MHz-8GHz Rayleigh surface acoustic wave.

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

[0161] In an implementable scheme, 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 logarithm of the interdigital electrodes is 10-100, and / or the width of the interdigital electrodes is 200nm-2000nm.

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

[0163] The working principle of the acousto-optic modulator with Bragg grating of the embodiment will be described below in combination with specific examples:

[0164] Based on the inverse piezoelectric coupling effect of lithium niobate film, the input microwave signal is converted into the surface acoustic wave signal of the lithium niobate film through the split interdigital transducer, so that the lithium niobate film appears a mechanical strain field distribution, and the mechanical acoustic wave generated on the surface of the lithium niobate film further acts on the chalcogenide optical waveguide. This process is based on the optomechanical coupling effect, so that the optical refractive index of the chalcogenide optical waveguide changes. Further, through the double-arm modulation mechanism of the symmetric Mach-Zehnder interferometer waveguide structure, the stress in the opposite direction is generated on the waveguide on both sides, the refractive index of the chalcogenide optical waveguide is changed, and the change of the refractive index is converted into the change of the phase. The optomechanical coupling effect includes moving boundary effect, photoelastic effect and electro-optic effect.

[0165] Meanwhile, the waveguide Bragg grating structure is directly involved in the process of acousto-optic modulation, and the generated acoustically-induced grating interacts with the static WBG by utilizing the characteristics of the interaction between the acoustic wave and the Bragg static grating. The acoustically-induced grating disturbs the phase and coupling condition of the static grating, which is equivalent to dynamically changing the effective refractive index or period of the Bragg static grating. The disturbance of the acoustically-induced grating causes a slight shift of the stop band. This causes the transmittance at the originally set laser wavelength on the edge of the stop band to change significantly, thereby causing the output light intensity to be strongly modulated. Meanwhile, the light wave can repeatedly reflect and diffract in the grating region, increasing the light intensity in this section and prolonging the residence time of the photons, converting weak acousto-optic effects into high-efficiency intensity modulation, and enhancing the acousto-optic coupling strength and the efficiency of acousto-optic modulation.

[0166] Meanwhile, the split interdigital transducer structure is adopted to effectively suppress the harmonic response, thereby expanding the working bandwidth. The acoustic reflection grating made of chalcogenide material is used to utilize the characteristics of high reflectivity of chalcogenide glass and strong acoustic field limitation, which is naturally compatible with the hybrid waveguide, to achieve synergistic enhancement and improve the utilization rate of acoustic energy. Thus, a new type of acousto-optic modulator with high modulation efficiency, large bandwidth, stable working state, and easier integration and manufacturing can be realized.

[0167] The acousto-optic modulator with a Bragg grating provided by the embodiment ingeniously utilizes the interaction between the acoustic wave and the static waveguide grating to convert weak acousto-optic effects into high-efficiency intensity modulation; the split interdigital transducer significantly improves the working bandwidth; meanwhile, the acoustic reflection grating made of chalcogenide glass material forms a restriction on the acoustic field strength. Meanwhile, an excellent balance between the modulation efficiency, coupling strength, bandwidth, stability, and complexity is achieved, and the acousto-optic modulator has the characteristics of high modulation efficiency, strong coupling strength, large bandwidth, high speed, stable working state, and easier integration and manufacturing, which is a very promising on-chip integrated acousto-optic modulation scheme.

[0168] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an illustration, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to the embodiments without departing from the principles and essence of the present disclosure, and these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. An acousto-optic modulator containing a Bragg grating, characterized in that, 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 a combined beam.

2. The acousto-optic modulator containing a Bragg grating as described in claim 1, characterized in that, 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.

3. The acousto-optic modulator containing a Bragg grating as described in claim 2, characterized in that, The interdigital transducer is a split-fin interdigital transducer; And / or, 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.

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

5. The acousto-optic modulator containing a Bragg grating as described in claim 3, characterized in that, The interdigitated transducer has an odd number of interdigitated fingers; And / or, 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.

6. The acousto-optic modulator containing a Bragg grating as described in claim 2, 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.

7. The acousto-optic modulator containing a Bragg grating as described in any one of claims 1-3, 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.

Images