Electro-optic modulator based on heterogeneous integrated platform of thin film electro-optical materials and preparation method thereof

Abstract

The present invention relates to the technical field of electro-optic modulators, and specifically to an electro-optic modulator based on a thin-film electro-optic material heterogeneous integration platform and a corresponding preparation method. The electro-optic modulator comprises a base wafer substrate, an electro-optic material thin film, an optical waveguide embedded in the electro-optic material thin film, the electro-optic material thin film is bonded to the base wafer substrate through a bonding layer, and then a coplanar stripline transmission line is arranged on the electro-optic material thin film. Compared with a traditional bulk material modulator, the electro-optic modulator effectively prevents leakage mode phenomenon at high frequencies by reducing the thickness of the electro-optic material, thereby increasing bandwidth and modulation efficiency; compared with a traditional thin film modulator, the electro-optic modulator has a higher yield and lower cost.

Description

Technical Field

[0001] The present invention relates to the technical field of electro-optic modulators, and in particular to an electro-optic modulator based on a heterogeneous integrated platform of thin-film electro-optic materials and a corresponding preparation method thereof. Background Art

[0002] In the field of modern optical communications and optical computing, the research and development of high-speed modulators is crucial. These modulators use lithium niobate (LiNbO 3 ), potassium dihydrogen phosphate (KDP), potassium titanium phosphate (KTP) or barium titanate (BaTiO 3 ) and other nonlinear optical materials, efficiently modulate radio frequency (RF) signals into optical signals, and achieve extremely high-speed data transmission and processing. This technological advancement has not only significantly improved the bandwidth and efficiency of optical communication systems, but also promoted the development of fiber-optic networks, optical computing, and high-speed Internet infrastructure. Especially in cutting-edge applications such as quantum computing and medical imaging, the performance of electro-optic modulators directly affects the performance of the system and the expansion of application scenarios.

[0003] As a key optoelectronic device, the design goals of electro-optic modulators include not only efficient photoelectric conversion and wide RF bandwidth (such as greater than 100 GHz), but also high energy efficiency in device configuration and operation. To achieve these goals, researchers are committed to optimizing the optical and electrical properties of materials, designing complex structures to maximize the electro-optic effect, and continuously improving manufacturing processes to improve device stability and reliability. Therefore, the development of electro-optic modulators is not only a reflection of technological progress, but also a key step in promoting communication technology to a new generation.

[0004] In view of the challenges of traditional electro-optical materials in the manufacture of photonic devices, especially in the application of electro-optical material integrated platforms, the existing processing technology has many limitations. At present, the design of electro-optic modulators is divided into two types: bulk materials and thin film materials, each of which has its own advantages and disadvantages.

[0005] The optical waveguide of the bulk electro-optic modulator is made by the proton diffusion method, but it has poor light field confinement ability and large RF loss. In addition, due to the excessive thickness of the substrate, the RF CPW mode is coupled with the substrate substrate mode, resulting in leakage mode, which reduces the bandwidth. Generally, the bandwidth of the bulk material modulator is less than 40GHz.

[0006] The thin-film electro-optical material integration platform uses wet etching, dry etching, optical-grade physical cutting, femtosecond laser and chemical mechanical polishing. In comparison, the thin-film modulator has improved the roughness of the waveguide interface and the transmission loss, and has a higher bandwidth, which can reach more than 100 GHz. However, the thin-film modulator has problems such as high cost, low yield, and mode mismatch with optical fiber, which limits its large-scale production and application.

[0007] In order to overcome these challenges and promote the development of photonic devices on the electro-optical material thin film platform, a new and suitable integration method for multiple materials is urgently needed. This method should not only take into account the chemical properties and stability of electro-optical materials, but also meet the requirements of modern optoelectronic devices for fine structure and high performance. Summary of the invention

[0008] The present invention is based on the problems of poor light field binding ability and reduced bandwidth caused by leakage mode in the current bulk electro-optic modulator using the traditional proton diffusion waveguide process, as well as the problems of high cost, low yield, mode mismatch with optical fiber in the electro-optic modulator of thin film materials, which limit the application of electro-optic materials. To this end, an electro-optic modulator based on a heterogeneous integration platform of thin film electro-optic materials is provided, and a corresponding preparation method is also provided. This is a high-performance electro-optic material photonic device, which shows great prospects and application potential in the field of photonic integration.

[0009] The technical solution adopted by the present invention to solve its technical problem is:

[0010] An electro-optic modulator based on a heterogeneous integrated platform of thin-film electro-optical materials, comprising:

[0011] Base wafer substrate, as a foundation, used to carry electro-optical material films and other carriers;

[0012] The electro-optic material film has a first side surface and a second side surface, an optical waveguide is embedded in one side of the first side surface, and the first side surface is arranged facing the base wafer substrate and in contact with a bonding layer arranged on the base wafer substrate; the thickness of the electro-optic material film satisfies the matching of the radio frequency signal speed and the light group speed to achieve relatively low insertion loss;

[0013] An optical waveguide is embedded in the electro-optical material film on a first side of the electro-optical material film;

[0014] A bonding layer, serving as a medium for connecting the electro-optical material film and the base wafer substrate, is used to bond the electro-optical material film to the base wafer substrate;

[0015] The coplanar waveguide transmission line is arranged on the second side surface of the electro-optical material film.

[0016] The key point of the present invention is to adopt the method of bulk material modulator, reduce the thickness of the traditional bulk material substrate from hundreds of microns to a few microns as an electro-optical material film, and directly make an optical waveguide on the electro-optical material film, thereby changing the structure of the electro-optic modulator, thereby reducing energy consumption, increasing bandwidth, improving modulation efficiency, and saving costs.

[0017] Further preferably, the thickness of the electro-optical material film is 1-10 microns.

[0018] Further preferably, the electro-optical material thin film material is selected from one of potassium dihydrogen phosphate, potassium dideuterium phosphate, lithium niobate, lithium tantalate, potassium titanyl phosphate and barium titanate.

[0019] Further preferably, the electro-optic modulator also includes a laser source, and an alignment groove is pre-formed by etching the base wafer substrate at a position corresponding to the optical waveguide, and the laser source eutectic is pasted in the alignment groove to ensure that the output light of the laser source is aligned with the optical waveguide.

[0020] Further preferably, the electro-optic modulator further comprises an input optical fiber and an output optical fiber, the base wafer substrate is prefabricated with a V-groove at a position corresponding to the optical waveguide, and the input optical fiber and the output optical fiber are fixed in the prefabricated V-groove and passively aligned with the optical waveguide.

[0021] Further preferably, the electro-optic modulator is a single-ended driven double-arm push-pull structure, comprising:

[0022] Input waveguide;

[0023] A beam splitter for dividing the input waveguide into at least two branches;

[0024] A waveguide modulation arm, wherein each branch waveguide modulation arm is used for modulating a signal;

[0025] A beam combiner, used for combining the output light beams of each waveguide modulation arm;

[0026] Output waveguide.

[0027] Further preferably, the electro-optic modulator adopts differential drive and a double-arm push-pull structure, including:

[0028] a differential driver for providing electrical signals of opposite phases;

[0029] The two modulation arms receive the positive and negative signals from the differential driver respectively.

[0030] Further preferably, the differential driver outputs to the anodes of the two modulation arms simultaneously to ensure reverse bias.

[0031] Further preferably, the signal electrodes of the two modulation arms share a DC bias voltage to achieve a shared bias structure.

[0032] The key point of the electro-optic modulator of the present invention is that it has a structural design difference from the traditional electro-optic modulator. Specifically, the traditional electro-optic modulator uses an ion or proton diffusion waveguide formed on the substrate crystal by ion exchange or proton diffusion process, which can effectively transmit optical signals. Among them, a buffer layer is used for speed matching, and the buffer layer can be SiO 2 , spin-on glass or polymer and other materials. And the base crystal thereof adopts one of potassium dihydrogen phosphate, deuterated potassium dihydrogen phosphate, lithium niobate, lithium tantalate, potassium titanyl phosphate and barium titanate. In the present invention, firstly, a base wafer substrate is adopted as the base, and the base wafer substrate adopts single crystal quartz, fused silica or silicon substrate. Then, a layer of electro-optical material film is bonded on the base wafer substrate through a bonding layer, and the electro-optical material film and the base wafer substrate form a heterogeneous integrated platform. This layer of electro-optical material film has a relatively thin thickness, and its raw material adopts one of potassium dihydrogen phosphate, deuterated potassium dihydrogen phosphate, lithium niobate, lithium tantalate, potassium titanyl phosphate and barium titanate. Then, an optical waveguide is formed on this layer of electro-optical material film, and the side of the electro-optical material film with the optical waveguide embedded therein is directly in contact with the base wafer substrate. Such a structure is in sharp contrast to the structure of traditional bulk material modulators. By reducing the thickness of the traditional substrate crystal from several hundred microns to less than 10 microns to form an electro-optical material film, such a film effectively prevents leakage mode phenomenon at high frequencies and improves the bandwidth; by increasing the overlapping area of ​​the modulated electric field and the optical mode field, the modulation efficiency is improved.

[0033] At present, the material systems that can be used for lithium niobate heterogeneous optoelectronic integration mainly include silicon, indium phosphide and periodically poled lithium niobate (PPLN). Lithium niobate is known as "optical silicon" for its excellent electro-optical and nonlinear optical properties, and its chemical properties are stable. The electro-optic modulator designed based on the superior electro-optical properties of thin-film lithium niobate has the advantages of low loss, ultra-high speed and ultra-high bandwidth. Periodically poled thin-film lithium niobate has important applications in the field of nonlinear optics, such as frequency conversion, optical parametric oscillation, optical rectification, etc. PPLN can significantly enhance nonlinear optical effects such as second harmonic generation (SHG) and difference frequency generation (DFG), and is a key material in the field of photonics and optical communications. The advantage of silicon photonics technology is that it has the characteristics of high integration and low cost with the help of decades of technological accumulation of silicon-based integrated circuits. The advantage of indium phosphide is that it can manufacture lasers and provide light sources in the communication band. Therefore, the best solution lies in the heterogeneous integration of multiple material systems to achieve complementary advantages.

[0034] Furthermore, the electro-optic modulator of the present invention eliminates the need for processing a mode spot converter by directly matching the optical waveguide mode with the optical fiber, and adopts a processing method similar to that of a bulk material modulator, thereby ensuring a higher yield and lower cost.

[0035] A method for manufacturing the above electro-optic modulator comprises the following steps:

[0036] Step 1: Prepare an embedded optical waveguide on an electro-optical material wafer by using a particle diffusion method or a proton exchange method;

[0037] Step 2: preparing a bonding layer on the base wafer substrate;

[0038] Step 3: Bonding the electro-optical material wafer with the embedded optical waveguide to the base wafer substrate through the bonding layer, and ensuring that the side where the optical waveguide is located is in contact with the bonding layer; specifically, aligning and pressurizing the electro-optical material wafer and the base wafer substrate through the fixture on the bonding machine, and using fusion bonding, eutectic bonding or epoxy bonding to bond the electro-optical material wafer to the base wafer substrate in a manner with low thermal stress and warpage; at the same time, after the above operations, performing corresponding post-processing, including UV or thermal curing to cure the bonding layer when epoxy bonding is used; finally, heat treating the bonded electro-optical material wafer to improve the stability of the bonding;

[0039] Step 4: performing thinning and polishing operations on the upper surface of the bonded electro-optical material wafer to reduce the thickness of the electro-optical material wafer to less than 10 μm, thereby forming an electro-optical material film;

[0040] Step 5: Form a metal coplanar waveguide transmission line on the polished surface of the electro-optical material film.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] Compared with the traditional bulk material modulator, firstly, this scheme effectively prevents the leakage mode phenomenon at high frequency by reducing the thickness of the electro-optical material, thereby improving the bandwidth; secondly, it omits the conventional buffer layer for velocity matching and improves the modulation efficiency by increasing the overlapping area of ​​the modulated electric field and the optical mode field;

[0043] Compared with traditional thin film modulators, firstly, the optical waveguide adopts a processing method similar to that of traditional bulk material modulators, ensuring a high yield and low cost; secondly, the optical waveguide mode is directly matched with the optical fiber, thus eliminating the need to process a mode spot converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1A A schematic diagram of the structure of the electro-optic modulator of the present invention is given.

[0045] Figure 1B Another schematic diagram of the structure of the electro-optic modulator of the present invention is given.

[0046] Figure 1C Another structural schematic diagram of the electro-optic modulator of the present invention is given.

[0047] Figure 1D Another structural schematic diagram of the electro-optic modulator of the present invention is given.

[0048] Figure 2A Given is a cross-sectional view of an electro-optic modulator of the present invention.

[0049] Figure 2B Given is a cross-sectional view of the thin film electro-optic material heterogeneous integrated platform electro-optic modulator of the present invention.

[0050] Figure 3A The graph shows the relationship between the electro-optic conversion response (S21) and the frequency characteristic of the electro-optic modulator of the present invention when lithium niobate is used as the electro-optic material.

[0051] Figure 3B The given is Figure 3A An example diagram of lithium niobate (LN) waveguide thickness and loss of the electro-optic modulator of the present invention at a frequency of 100 GHz.

[0052] Figure 4 Presented are cross-sectional views of an exemplary electro-optic modulator at various stages of an exemplary method of wafer-substrate bonding and thinning.

[0053] Figure 5A A schematic diagram of the side view structure of a packaged electro-optic modulator is given.

[0054] Figure 5B Shows Figure 5A Diagram of the coupling method from the optical fiber to the modulator optical waveguide.

[0055] Figure 5C Shows Figure 5A Diagram of the coupling method from the laser to the modulator optical waveguide.

[0056] In the figure:

[0057] 101 driver, 102 input waveguide, 103 waveguide modulation arm, 104 output waveguide, 105 signal electrode, 106 fixed potential electrode;

[0058] 201 substrate crystal, 202 buffer layer, 203 ion or proton diffusion waveguide, 204 modulation signal electrode, 205 ground electrode;

[0059] 301 base wafer substrate, 302 electro-optical material film, 303 bonding layer, 304 optical waveguide, 305 coplanar waveguide transmission line, 306 ground transmission line;

[0060] 401 electro-optical material wafer, 402 fixture, 403 printed circuit board, 404 input optical fiber, 405 output optical fiber, 406 continuous wave laser, 407 photodetector, 408 prefabricated solder. DETAILED DESCRIPTION

[0061] The technical scheme of the present invention is further described in detail below through specific embodiments. In the present invention, unless otherwise specified, the methods in the following embodiments are all conventional methods in the art.

[0062] Example:

[0063] The present invention provides an electro-optic modulator based on a heterogeneous integrated platform of thin-film electro-optical materials. The basic structure of the electro-optic modulator is as follows:

[0064] include:

[0065] Base wafer substrate 301, as a foundation, used to carry electro-optical material film 302 and other carriers;

[0066] The electro-optic material film 302 has a first side surface and a second side surface, an optical waveguide 304 is embedded in one side of the first side surface, and the first side surface is arranged facing the base wafer substrate 301 and in contact with the bonding layer 303 arranged on the base wafer substrate 301; the thickness of the electro-optic material film 302 satisfies the matching of the radio frequency signal speed and the light group speed to achieve relatively low insertion loss, and the thickness of the electro-optic material film 302 is 5 microns; the electro-optic material film 302 is thinned from the bulk material wafer to a thickness of several microns by chemical mechanical polishing (CMP); the material of the electro-optic material film 302 is selected from one of potassium dihydrogen phosphate, deuterated potassium dihydrogen phosphate, lithium niobate, lithium tantalate, potassium titanyl phosphate and barium titanate;

[0067] The optical waveguide 304 is embedded in the electro-optical material film 302 at a first side surface of the electro-optical material film 302;

[0068] The bonding layer 303 is used as a medium for connecting the electro-optic material film 302 and the base wafer substrate 301, and is used to bond the electro-optic material film 302 to the base wafer substrate 301; the bonding layer 303 includes a polymer-based material or a dielectric-based material;

[0069] The coplanar waveguide transmission line 305 is arranged on the second side surface of the electro-optical material film 302. The coplanar waveguide transmission line is made of gold (Au) or other suitable metal materials. Other metals include aluminum, silver, titanium, etc.

[0070] In addition, the electro-optic modulator further comprises a laser source. The base wafer substrate 301 is etched with an alignment groove at a position corresponding to the optical waveguide 304 . The laser source eutectic is mounted in the alignment groove to ensure that the output light of the laser source is aligned with the optical waveguide 304 .

[0071] Meanwhile, the electro-optic modulator further comprises an input optical fiber 404 and an output optical fiber 405 . The base wafer substrate 301 is prefabricated with a V-groove at a position corresponding to the optical waveguide 304 . The input optical fiber 404 and the output optical fiber 405 are fixed in the prefabricated V-groove and passively aligned with the optical waveguide 304 .

[0072] The electro-optic modulator is a single-ended driven double-arm push-pull structure, comprising:

[0073] Input waveguide 102;

[0074] A beam splitter, for dividing the input waveguide 102 into at least two branches;

[0075] A waveguide modulation arm 103, wherein each branch of the waveguide modulation arm 103 is used for modulating a signal;

[0076] A beam combiner, used to combine the output light beams of each waveguide modulation arm 103;

[0077] Output waveguide 104 .

[0078] The electro-optic modulator adopts differential drive and double-arm push-pull structure, including:

[0079] A differential driver 101 is used to provide electrical signals with opposite phases; the differential driver 101 outputs to the anodes of the two modulation arms simultaneously to ensure reverse bias;

[0080] The two modulation arms receive positive and negative signals from the differential driver 101 respectively; the signal electrodes 105 of the two modulation arms share a DC bias voltage to realize a shared bias structure.

[0081] A method for manufacturing the electro-optic modulator, as Figure 4 As shown, the method comprises the following steps:

[0082] Step 1: using a particle diffusion method or a proton exchange method to prepare an embedded optical waveguide 304 on an electro-optical material wafer 401;

[0083] Step 2: Prepare a bonding layer 303 on a base wafer substrate 301; the base wafer substrate 301 is made of single crystal quartz, fused silica or silicon substrate.

[0084] Step 3: Bond the electro-optical material wafer 401 with the embedded optical waveguide 304 to the base wafer substrate 301 through the bonding layer 303, and ensure that the side where the optical waveguide 304 is located is in contact with the bonding layer 303; specifically, align and pressurize the electro-optical material wafer 401 and the base wafer substrate 301 through the clamp 402 on the bonding machine, and bond the electro-optical material wafer 401 to the base wafer substrate 301 in a manner with low thermal stress and warpage. Different bonding methods are selected for bonding, such as fusion bonding, eutectic bonding or epoxy bonding. At the same time, after the above operations, corresponding post-processing is performed. For example, when epoxy bonding is used, UV or thermal curing is also required to cure the bonding layer 303; finally, the bonded electro-optical material wafer 401 is heat-treated as needed to improve the stability of the bonding;

[0085] Step 4: Thinning and polishing the upper surface of the bonded electro-optical material wafer 401 to reduce the thickness of the electro-optical material wafer 401 from about 500 μm to several microns, specifically to less than 10 μm, to form an electro-optical material film 302;

[0086] Step 5: Finally, a metal coplanar waveguide transmission line 305 is formed on the polished surface of the electro-optical material film 302 .

[0087] The electro-optic modulator of the present invention is further described in detail below.

[0088] like Figure 1A As shown, this is an electro-optic modulator based on the above structure, which adopts a single-ended drive balanced structure. It includes a driver 101 and a power supply terminal Vdd, and its optical waveguide 304 includes an input waveguide 102, a beam splitter connected to the input waveguide 102, a waveguide modulation arm 103 arranged at each branch of the beam splitter, a beam combiner connected to each waveguide modulation arm 103, and an output waveguide 104 connected to the beam combiner. A signal electrode 105 and a fixed potential electrode 106 are respectively provided on both sides of each waveguide modulation arm 103.

[0089] Among them, the beam splitter can divide the input waveguide 102 into at least two branches, and the waveguide modulation arm 103 of each branch can be used to modulate the signal. The optical signal is input from the input waveguide 102, and is divided into at least two beams of light by the beam splitter. The light beams split by the beam splitter enter the waveguide modulation arm 103 respectively. The signal electrode 105 and the two fixed potential electrodes 106 load the modulation signal onto the waveguide modulation arm 103 to change the effective refractive index of the waveguide modulation arm 103, thereby changing the phase difference between the optical signals transmitted in each waveguide modulation arm 103 to achieve modulation of the optical signal. In the figure, Vdd is a DC bias voltage. The fixed potential electrode 106 is connected to the power supply terminal Vdd through a resistor R to ensure the stability of the reverse bias. Compared with the modulator of the single-drive unbalanced mode, the single-ended drive balanced structure of the present invention can reduce or eliminate signal chirp in this balanced drive mode.

[0090] To drive the diode, the electro-optic thin film modulator needs to provide an alternating current (AC) modulation signal and an appropriate direct current (DC) bias. In the conventional electro-optic material Mach-Zehnder modulator (MZM), the driver 101 is able to provide a high (greater than 5V) peak voltage swing, making it competitive in long-distance high extinction ratio transmission. However, this single-ended driving method is incompatible with the CMOS driver 101 due to its low power supply voltage Vdd and breakdown stress. In order to maintain a reasonable extinction ratio, a push-pull structure modulator is required to increase the effective length of the modulator. The basic idea of ​​the push-pull structure is to double the effective phase shift near the common mode level (i.e., the quadrature point) by applying opposite phase drives to the two arms. Since the electrical signals on the two arms are opposite, a positive voltage is applied to one arm and a negative voltage is applied to the other arm. This design can effectively improve the linearity of the modulation and reduce distortion. Finally, the two phase-modulated light waves are recombined and interfered at the output end to produce a modulated optical signal. The push-pull Mach-Zehnder modulator (MZM) is widely used in high-performance optical communication systems due to its high linearity, low distortion and excellent modulation effect.

[0091] To reduce the number of biases, a differential driver 101 can be used to output to the anodes of the two modulation arms simultaneously. Since their cathodes are connected to the highest DC voltage Vdd, the reverse bias is well guaranteed. The DC bias electrodes can be placed separately (such as Figure 1D As shown), it can also be shared by two signal electrodes 105 (as shown Figure 1B and 1C In these cases, the drive swing on each modulation arm is Vs, and the effective phase shift length is doubled, thus achieving a push-pull structure.

[0092] like Figure 1B As shown, this is based on Figure 1AAnother schematic diagram of the structure of the electro-optic modulator in the structure Figure 1A The difference is that in this structure, a differential driving method is adopted. Specifically, the electro-optic modulator of this structure includes a driver 101 and a power supply terminal Vdd, wherein the driver 101 has a positive and negative signal input terminal, can amplify the input signal, and output the amplified signal to the signal electrode 105 and two fixed potential electrodes 106 respectively. The signal electrode 105 and the fixed potential electrode 106 are respectively connected to the power supply terminal Vdd, and at the same time, resistors R1, R2 and R3 are provided between the fixed potential electrode 106 and the power supply terminal Vdd. In practical applications, the optical signal enters from the input waveguide 102, is divided into multiple beams of light by the beam splitter, and enters their respective waveguide modulation arms 103. After the driver 101 amplifies the input positive and negative signals, it is loaded onto the signal electrode 105 and the fixed potential electrode 106 respectively, thereby modulating the optical signal. Through this differential driving method, the performance of the modulator can be effectively improved, the distortion can be reduced, and the modulation effect can be enhanced.

[0093] like Figure 1C As shown, this is another electro-optic modulator based on the structure of the present invention. Figure 1B The electro-optic modulator in FIG. 1 is similar to the electro-optic modulator in FIG. 1 , except that the electro-optic modulator adopts a design of differential drive, double-arm push-pull and shared bias. Specifically, the electro-optic modulator includes a driver 101, which has positive and negative signal input terminals, can amplify the input signal, and output the amplified signal to the signal electrode 105 (S-) and the signal electrode 105 (S+) respectively. The optical signal enters from the input waveguide 102, is divided into multiple beams of light by the beam splitter, and enters the respective waveguide modulation arms 103. In this structure, the signal electrodes 105 of the two modulation arms share a DC bias voltage Vdd. The positive and negative signals output by the driver 101 are respectively loaded on the S+ and S- electrodes, thereby phase modulating the optical signal. Since the electrical signals of the two modulation arms are opposite, the modulation effect is doubled, which effectively improves the linearity and extinction ratio of the modulator, and reduces distortion. The two light waves after phase modulation are recombined and interfered at the output end, and the modulated optical signal is output from the output waveguide 104. This design not only simplifies the circuit structure, but also improves the performance of the electro-optic modulator, and is suitable for high-performance optical communication systems. In the figure, the fixed potential electrode 106 is connected to the power supply terminal Vdd through a resistor R to ensure the stability of the reverse bias.

[0094] like Figure 1D As shown, this is another electro-optic modulator based on the structure of the present invention. Figure 1B and Figure 1CThe structure of is similar to that of , using differential drive and double-arm push-pull structure, but the difference is that the DC bias electrodes are placed separately. Specifically, the electro-optic modulator includes a driver 101, which has positive and negative signal input terminals, which are respectively connected to two signal electrodes 105, and the two signal electrodes 105 are S+ and S-, respectively, and can amplify the input signal and output the amplified signal to the signal electrodes 105. The optical signal enters from the input waveguide 102, is divided into multiple beams of light by the beam splitter, and enters the respective waveguide modulation arms 103. In this structure, the positive and negative signals output by the driver 101 are respectively loaded onto the signal electrode 105 (S+) and the signal electrode 105 (S-) electrodes, thereby phase modulating the optical signal. Since the electrical signals of the two modulation arms are opposite, the modulation effect is doubled, which effectively improves the linearity and extinction ratio of the modulator, while reducing distortion. The two beams of light waves that have undergone phase modulation are recombined and interfered at the output end (output waveguide 104) to generate a modulated optical signal. This design improves the stability and performance of the modulator by placing the DC bias electrodes separately, and is suitable for high-performance optical communication systems. At the same time, in this structure, the two fixed potential electrodes 106 are connected to the power supply terminal Vdd through resistors R1 and R2 to ensure the stability of the reverse bias.

[0095] like Figure 2A As shown, this is a cross-sectional view of a conventional ion exchange optical waveguide 304 structure, which includes a substrate crystal 201, and an ion or proton diffusion waveguide 203 formed on the substrate crystal 201 by an ion exchange or proton diffusion process, which can effectively conduct optical signals. The buffer layer 202 is used for speed matching and can be SiO 2 , spin-coated glass or polymer. The modulation signal electrode 204 is used to modulate the signal, and the ground electrode 205 is used to provide a fixed potential. Affected by the processing technology, the electrode often has an inverted trapezoidal structure. The material of the substrate crystal 201 can be selected from a variety of different optical crystal materials, such as KDP (potassium dihydrogen phosphate), DKDP (deuterated potassium dihydrogen phosphate), LiNbO 3 (Lithium Niobate), LiTaO 3 (lithium tantalate), KTP (potassium titanyl phosphate) or BaTiO 3 (barium titanate), etc. These materials have excellent properties in optical and nonlinear optical applications.

[0096] like Figure 2B As shown, Figure 2B The structure of the improved optical waveguide 304 of the present invention is shown in cross-sectional view. The figure shows a cross-sectional view of an electro-optic modulator arranged along the optical signal propagation axis in the modulation region. Figure 2BAs shown, the electro-optic modulator is formed on a base wafer substrate 301, which can be single crystal quartz, fused silica or a silicon substrate. The electro-optic modulator also includes a bonding layer 303 disposed on the base wafer substrate 301. The bonding layer 303 can be composed of different types of polymer-based materials, such as ultraviolet (UV) epoxy resin, benzocyclobutene (BCB) polymer, SU-8 polymer, dry film photoresist, bonding sheet, etc. The bonding layer 303 can also include a dielectric-based material, such as SiO 2 / SiN x O y Si nanobonder in the middle layer, or SiO bonded by fusion bonding 2 / SiN x O y Intermediate layer or other material.

[0097] The electro-optic modulator includes an electro-optic material film 302 and an optical waveguide 304 embedded therein. The electro-optic material film 302 is located on a bonding layer 303, that is, the bonding layer 303 is used to bond the electro-optic material film 302 to a base wafer substrate 301. The optical waveguide 304 can be formed by processes such as particle diffusion or proton exchange. The electro-optic modulator also includes a signal transmission line, i.e., a coplanar waveguide transmission line 305 and its associated first and second ground transmission lines 306, located on the upper surface of the electro-optic material film 302. The coplanar waveguide transmission line 305 can be made of any suitable electrical conductor material, such as gold (Au) or other suitable metals.

[0098] Since the electro-optic material film 302 is not formed by ion slicing, but by thinning the bulk material wafer to a thickness of several microns by chemical mechanical polishing (CMP), the mode field diameter (MFD) of the optical waveguide 304 of the electro-optic modulator can directly match the single-mode optical fiber without the need for a mode converter, thereby reducing processing complexity and improving chip yield.

[0099] like Figure 3A As shown, Figure 3AAn example graph of the normalized electro-optical (E2O) conversion response (S21) of a modulator using lithium niobate as an electro-optical material film 302 relative to frequency characteristics is given. In the figure, the horizontal axis represents frequency in gigahertz (GHz) ranging from 0 GHz to 100 GHz; the vertical axis represents the S21 parameter in decibels (dB). As shown in the figure, the S21 characteristics of lithium niobate (LN) films with thicknesses of 6.8μm to 8.2μm are given as a function of frequency. Among these characteristics, when the LN film thickness is 7.4μm, the insertion loss of the modulator is significantly reduced (e.g., less than 3dB) over a wider bandwidth (e.g., greater than 100GHz). When the LN film thickness makes the RF signal speed substantially match the optical group velocity, a relatively low modulator insertion loss can be achieved. Similarly, when other electro-optical material films 302 are used, the film thickness also needs to be optimized to achieve the maximum bandwidth.

[0100] like Figure 3B As shown, Figure 3B Given about Figure 3A The relationship between S21 and lithium niobate (LN) waveguide thickness at 100 GHz for the electro-optic modulator in FIG. In the figure, the horizontal axis represents the thickness variation range of the LN film in micrometers (μm), and the vertical axis represents the S21 parameter in decibels (dB). As shown in the figure, when the thickness of the LN film is 7.4μm, S21 reaches a minimum value (for example, about -2.3dB), indicating that the insertion loss is the smallest at this time. This result is consistent with the thickness that causes the RF signal speed to basically match the optical group velocity, indicating that optimizing the thickness of the LN film can significantly improve the performance of the electro-optic modulator.

[0101] The electro-optic modulator made of lithium niobate as the material of the electro-optic material film 302 and the specific structure of the present invention can be tested for its specific performance. Figure 3A and 3B It can be seen that the performance of the electro-optic modulator of the present invention is far higher than the bandwidth of the traditional bulk material lithium niobate.

[0102] Therefore, it can be determined that the performance of the electro-optic modulator of the present invention is greatly improved compared with the traditional electro-optic modulator.

[0103] like Figure 5A As shown, Figure 5A A side view of a packaged electro-optic modulator is shown. Figure 5AIn the figure, first, there is a printed circuit board 403 (PCB), on which a base wafer substrate 301 is arranged, on which an electro-optical material film 302 is indirectly arranged, and on both sides of the base wafer substrate 301, optional input optical fibers 404 and output optical fibers 405 are arranged, and on the base wafer substrate 301, a continuous wave (CW) laser, a driver 101, and a photodetector 407 (PD) are arranged. Among them, the continuous wave (CW) laser, the driver 101, and the photodetector 407 (PD) are all optional components, which can be bonded to the surface of the modulator chip by flip chip bonding technology.

[0104] like Figure 5B As shown, Figure 5B Given in Figure 5A A coupling method from an optical fiber to a modulator optical waveguide 304. At the input / output end of the modulator chip, a V-groove is formed by precision cutting, and the input optical fiber 404 or the output optical fiber 405 can be fixed in the V-groove with UV glue to achieve passive alignment with the modulator optical waveguide 304. In the figure, the electro-optical material film 302 is bonded to the base wafer substrate 301 through a bonding layer 303, and an optical waveguide 304 is arranged on the electro-optical material film 302. This method can achieve efficient and high-precision optical fiber coupling, and improve coupling efficiency and integration.

[0105] like Figure 5C As shown, Figure 5C Given about Figure 5A A coupling method of a laser to a modulator optical waveguide 304 in the figure. The figure includes a continuous wave laser 406 (e.g., a distributed feedback (DFB) laser), which is connected to a base wafer substrate 301 through, for example, pre-made solder 408. The continuous wave laser 406 as a laser source can be located in an alignment groove etched in the base wafer substrate 301, so that the optical aperture of the continuous wave laser 406 is basically aligned with the optical waveguide 304 of the electro-optical material film 302 bonded to the base wafer substrate 301 through the bonding layer 303. In this way, efficient alignment and coupling of the laser output optical signal with the electro-optic modulator optical waveguide 304 is achieved, thereby improving the optical signal transmission efficiency and system integration.

[0106] The electro-optic modulator of the present invention is different from the conventional bulk electro-optic modulator which usually uses V-grooves to input and output optical signals from optical fibers. The electro-optic modulator of the present invention adopts a coupling scheme of a heterogeneous integrated electro-optic modulator. Specifically, Figure 5B As shown in FIG. 1 , this is a solution for integrating the V-groove into the chip. Figure 5C As shown, this is a solution to integrate the light source onto the chip.

[0107] The integration scheme of the present invention improves the integration level, and its advantages are as follows:

[0108] Reduced optical loss: By integrating the V-groove and light source directly onto the chip, the coupling loss of the optical signal during transmission can be reduced, thus improving the overall efficiency of the system.

[0109] Reduce packaging complexity: Traditional fiber coupling and light source coupling methods require complex packaging processes, while integrated solutions simplify this process and reduce packaging complexity and cost;

[0110] Improve system stability: The integrated design reduces the optical signal loss caused by mechanical alignment errors and improves the stability and reliability of the system;

[0111] Reduce device size: Integrated design can effectively reduce the overall size of the device, making it more suitable for miniaturized and portable applications;

[0112] Improved manufacturing yield: Integrated design helps improve the yield in the manufacturing process by reducing the number of independent components and alignment steps;

[0113] Enhanced functional integration: Integrating V-grooves and light sources onto the chip can enable the integration of more functions, laying the foundation for future multifunctional integrated photonic chips.

[0114] It is obvious to those skilled in the art that the above embodiments are not intended to be exhaustive or limit the embodiments to the specific precise forms disclosed. It is obvious to those skilled in the art that certain modifications, combinations and variations can be made based on the above teachings.

Claims

1. An electro-optic modulator based on a heterogeneous integrated platform of thin-film electro-optical materials, characterized in that: include: Base wafer substrate, as a foundation, used to carry electro-optical material films and other carriers; The electro-optic material film has a first side surface and a second side surface, an optical waveguide is embedded in one side of the first side surface, and the first side surface is arranged facing the base wafer substrate and in contact with a bonding layer arranged on the base wafer substrate; the thickness of the electro-optic material film satisfies the matching of the radio frequency signal speed and the light group speed to achieve relatively low insertion loss; An optical waveguide is embedded in the electro-optical material film on a first side of the electro-optical material film; A bonding layer, serving as a medium for connecting the electro-optical material film and the base wafer substrate, is used to bond the electro-optical material film to the base wafer substrate; A coplanar waveguide transmission line is arranged on the second side of the electro-optical material film; The thickness of the electro-optical material film is 5-10 microns; The electro-optic modulator also includes a laser source, and the base wafer substrate is etched to pre-form an alignment groove at a position corresponding to the optical waveguide, and the laser source eutectic is pasted in the alignment groove to ensure that the output light of the laser source is aligned with the optical waveguide; The electro-optic modulator further comprises an input optical fiber and an output optical fiber, the base wafer substrate is prefabricated with a V-shaped groove at a position corresponding to the optical waveguide, the input optical fiber and the output optical fiber are fixed in the prefabricated V-shaped groove, and are passively aligned with the optical waveguide; The electro-optic modulator adopts differential drive and double-arm push-pull structure, including: a differential driver for providing electrical signals of opposite phases; Two modulation arms, receiving positive and negative signals from the differential driver respectively; The differential driver outputs to the anodes of the two modulation arms simultaneously to ensure reverse bias; The differential driver has positive and negative signal input terminals, which are respectively connected to two signal electrodes, the two signal electrodes are S+ and S-, and can amplify the input signal and output the amplified signal to the signal electrodes respectively.

2. The electro-optic modulator according to claim 1, characterized in that: The material of the electro-optical material film is selected from one of potassium dihydrogen phosphate, potassium dideuterium phosphate, lithium niobate, lithium tantalate, potassium titanyl phosphate and barium titanate.

3. The electro-optic modulator according to claim 1, characterized in that: The signal electrodes of the two modulation arms share a DC bias voltage to realize a shared bias structure.

4. A method for manufacturing an electro-optical modulator according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Prepare an embedded optical waveguide on an electro-optical material wafer by using a particle diffusion method or a proton exchange method; Step 2: preparing a bonding layer on the base wafer substrate; Step 3: Bonding the electro-optical material wafer with the embedded optical waveguide to the base wafer substrate through the bonding layer, and ensuring that the side where the optical waveguide is located is in contact with the bonding layer; specifically, aligning and pressurizing the electro-optical material wafer and the base wafer substrate through the fixture on the bonding machine, and using fusion bonding, eutectic bonding or epoxy bonding to bond the electro-optical material wafer to the base wafer substrate in a manner with low thermal stress and warpage; at the same time, performing corresponding post-processing, including UV or thermal curing to cure the bonding layer when epoxy bonding is used; finally, heat treating the bonded electro-optical material wafer to improve the stability of the bonding; Step 4: performing thinning and polishing operations on the upper surface of the bonded electro-optical material wafer to reduce the thickness of the electro-optical material wafer to less than 10 μm, thereby forming an electro-optical material film; Step 5: Form a metal coplanar waveguide transmission line on the polished surface of the electro-optical material film.

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