Preparation method of on-chip modulator and palladium diselenide photoelectric detector integrated chip

Abstract

The invention discloses a preparation method of an on-chip modulator and palladium diselenide photoelectric detector integrated chip, which is characterized in that a lithium niobate intensity electro-optical modulator with an MZ interferometer configuration is connected with an on-chip photoelectric detector based on a palladium diselenide material through a lithium niobate waveguide; a high-performance electro-optical modulator and a high-sensitivity PdSe2 detector are integrated in a monolithic mode, and the modulation process of converting an electric signal into an optical signal and the detection process of converting the optical signal into the electric signal are achieved on a chip. Compared with the prior art, the device has the advantages of being compact in structure, small in size, rapid in response, high in bandwidth, low in power consumption and the like, the synchronization function of on-chip electro-optical modulation and photoelectric detection can be achieved in a communication band, the 3 dB bandwidth of an integrated system exceeds 2 GHz, the response rate of an on-chip detector exceeds 0.3 A / W, and the power consumption is low. A high-performance and high-integration-level on-chip solution is provided for the leading-edge fields of high-speed optical communication, photon calculation, neural networks and the like, and wide application prospects are achieved in the fields of optical communication, sensing, integrated photoelectric chips and the like.

Description

Technical Field

[0001] This invention relates to the fields of optical communication and integrated photonic devices, and in particular to a method for fabricating an integrated chip of a lithium niobate on-chip modulator and a palladium diselenide photodetector. Background Technology

[0002] Based on the high speed, wide bandwidth, and low power consumption characteristics of photons, optical information processing platforms relying on photonic integrated circuits are expected to become a core technology of the next generation of information technology. The core of photonic integrated circuits lies in achieving breakthroughs in physical principles to realize multiple functions, including light sources, modulators, photodetectors, and on-chip optical interconnects, within micro- and nano-photonic structures, and integrating them on the same substrate to form modules or even systems. Lithium niobate possesses excellent physical and chemical stability, a wide optical low-loss window (0.35-5 μm), excellent nonlinear effects, and a high electro-optic coefficient, making it an ideal photonic platform for fabricating high-speed programmable photonic integrated chips. In particular, the mass production of lithium niobate-on-insulator (LNOI) wafers in the last fifteen years has spurred the rapid development of lithium niobate-based photonics.

[0003] Currently, highly integrated passive photonic devices such as high-quality factor optical micro / nano resonators, low-loss optical waveguides, and high-efficiency nonlinear optical frequency converters have been successfully realized at LNOI. Lithium niobate electro-optic modulators utilize the strong electro-optic effect of lithium niobate to load external microwave signals into a laser, enabling the control of characteristic parameters such as intensity, phase, and frequency. Photodetectors are devices where laser light enters a photosensitive material via a lithium niobate waveguide under evanescent wave coupling, converting the optical signal into an electrical signal through the photoelectric effect.

[0004] In summary, existing technologies cannot meet the synchronization function of on-chip electro-optic modulation and photoelectric detection, and cannot realize the modulation process of converting electrical signals into optical signals and the detection process of converting optical signals into electrical signals. Summary of the Invention

[0005] The purpose of this invention is to provide a method for fabricating an integrated chip of an on-chip modulator and a palladium diselenide photodetector, addressing the shortcomings of existing technologies. This method employs a lithium niobate intensity electro-optic modulator with a Mach-Zehnder interferometer configuration and an on-chip photodetector based on palladium diselenide, connected via a lithium niobate waveguide. This enables on-chip modulation of electrical signals into optical signals and detection of optical signals into electrical signals. The on-chip detector has a responsivity exceeding 0.3 A / W and an integrated bandwidth exceeding 2 GHz, offering advantages such as simple fabrication process, small size, and high bandwidth. This method utilizes photolithography-assisted chemical mechanical polishing to fabricate an integrated chip of an on-chip modulator and a two-dimensional material photodetector on a lithium niobate-on-insulator substrate. This integrated chip can perform individual laser modulation and detection, as well as on-chip transmission of electrical signals into optical signals and back into electrical signals. It possesses comprehensive advantages of compact structure, fast response, and low power consumption, providing a high-performance, highly integrated on-chip solution for cutting-edge fields such as high-speed optical communication, photonic computing, and neural networks. It has broad application prospects in optical communication, sensing, and integrated optoelectronic chips.

[0006] The specific technical solution to achieve the objective of this invention is: a method for fabricating an integrated chip of an on-chip modulator and a palladium diselenide photodetector, characterized by using a method for fabricating an integrated chip of an on-chip modulator and a two-dimensional material photodetector on a lithium niobate substrate, realizing the modulation process of converting electrical signals into optical signals and the detection process of converting optical signals into electrical signals on-chip. This method includes the following specific steps: Step 1: Structural Design of Thin-Film Lithium Niobate Modulator Integrated with PdSe2 Detector The thin-film lithium niobate modulator and detector integrated chip design consists of an on-chip lithium niobate modulator, a PdSe2 photodetector, and an optical waveguide. First, the on-chip lithium niobate modulator is designed using a Mach-Zehnder (MZ) interferometer configuration. The modulator structure is simulated using Lumerical software, and the thickness, spacing, and length of the modulator electrodes are optimized to achieve a theoretical bandwidth exceeding 10 GHz. Next, the on-chip detector structure is designed. To improve the evanescent wave coupling efficiency between the PdSe2 material and the laser within the optical waveguide, the thickness of the detector electrodes and the material are optimized. Furthermore, to improve the separation and collection speed of photogenerated carriers in the detector, the spacing and shape of the detector electrodes are optimized. Finally, the optical waveguide connecting the two devices is designed, including a straight waveguide and two curved waveguides, with optimized bending radii to minimize light intensity loss. Based on the above design, the design layout of the lithium niobate waveguide can be obtained, which includes the lithium niobate modulator waveguide and electrodes, the PdSe2 detector waveguide and electrodes, and the straight and curved waveguides. Step 2: Fabrication of a thin-film lithium niobate modulator integrated with a PdSe2 detector 1) Take a lithium niobate substrate on an insulator, which mainly consists of three layers: the bottom layer is a silicon substrate about 100 micrometers thick, with a silicon dioxide layer of a few micrometers on its upper surface, and a thin film of lithium niobate on the upper surface of the silicon dioxide layer; deposit a chromium film on the lithium niobate film, and use photolithography to prepare a mask pattern with a specific structure. 2) The design waveguide layout of the thin-film lithium niobate modulator and PdSe2 detector integrated chip is converted into a photolithographic layout, and a femtosecond laser is used to write on a chromium mask on the substrate to obtain a waveguide mask containing an integrated chip consisting of a modulator waveguide, a detector waveguide, and a bent waveguide. 3) The substrate with the mask is polished and etched using chemical mechanical polishing to transfer the mask pattern onto the thin film lithium niobate. Then, the chromium mask on the surface of the substrate is etched away using a chromium etching solution to obtain an integrated chip waveguide structure consisting of a modulator waveguide, a detector waveguide, and a bent waveguide. 4) Metal coating is performed on the waveguide of the integrated chip using magnetron sputtering, and then femtosecond laser is used to write on the metal mask of the substrate to obtain an electrode mask containing an integrated chip consisting of modulator electrodes and detector electrodes. 5) Use an etching solution to etch away the unprotected metal on the substrate surface, and then use an acid or alkali solution to clean the substrate to obtain the electrode structure of the integrated chip consisting of modulator electrodes and detector electrodes. 6) Polish the end face of the lithium niobate modulator and detector integrated chip by chemical mechanical polishing; 7) The palladium diselenide substrate was repeatedly peeled off using Scottish tape. Materials of suitable size and thickness were then transferred to the detector electrode of the integrated chip using the PDMS dry transfer method. This resulted in the fabrication of an integrated chip consisting of a lithium niobate on-chip modulator, a PdSe2 photodetector, and an optical waveguide.

[0007] The integrated chip for the lithium niobate on-chip modulator and palladium diselenide photodetector includes a lithium niobate electro-optic intensity modulator, a palladium diselenide photodetector, and a bent waveguide with radius R. The materials used for the modulator and photodetector include lithium niobate, silicon dioxide, silicon, gold, chromium, and palladium diselenide. The integrated chip integrates the lithium niobate electro-optic intensity modulator and the palladium diselenide photodetector, enabling on-chip transmission from electrical signals to optical signals and back to electrical signals. The bandwidth of a single modulator reaches 10 GHz, and the integrated bandwidth exceeds 2 GHz.

[0008] Compared with the prior art, the present invention has the following beneficial technical effects and significant technical progress: 1) For the first time, an electro-optic intensity modulator and a palladium diselenide photodetector are integrated on lithium niobate; 2) The fabrication process is simple, with only one coating and processing required for both the modulator electrode and the detector electrode; 3) By separating the on-chip distance between the modulator and the detector and by shielding them, high-frequency crosstalk noise can be effectively suppressed; 4) The palladium diselenide photodetector has a bandwidth exceeding 2 GHz and a responsivity exceeding 0.3 A / W; 5) Its combined advantages of compact structure, fast response, and low power consumption provide a high-performance, highly integrated on-chip solution for cutting-edge fields such as high-speed optical communication, photonic computing, and neural networks. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the structure of a palladium diselenide detector; Figure 3 The response rate curve of the palladium diselenide detector prepared in Example 1 is shown. Figure 4 The bandwidth curve of the electro-optic modulator and photodetector monolithically integrated in Example 1 is shown. Detailed Implementation

[0010] This invention integrates a high-performance electro-optic modulator and a high-sensitivity PdSe2 detector monolithically on a lithium niobate-on-insulator platform using micro-nano fabrication technology, and employs a one-time electrode fabrication process, significantly improving process compatibility and large-scale fabrication potential. This device can achieve on-chip electro-optic modulation and photodetection synchronization in the communication band (e.g., 1550 nm), with an integrated system bandwidth exceeding 2 GHz (3 dB bandwidth). Its fabrication specifically includes the following steps: Step 1: Structural design of the integrated chip for the thin-film lithium niobate modulator and PdSe2 detector Step 1-1: Design an on-chip modulator for lithium niobate using a Mach-Zehnder interferometer configuration. Simulate the modulator structure using Lumerical software. Optimize the electrode thickness, spacing, and length of the modulator using scanning parameter simulation to achieve a theoretical bandwidth exceeding 10 GHz. Steps 1-2: Design the on-chip detector structure and use scanning parameter simulation to optimize the electrode spacing and shape of the detector in order to improve the carrier transport efficiency generated by PdSe2 material; Steps 1-3: Design straight and curved waveguides to connect the two devices, resulting in an integrated chip design layout including: a lithium niobate modulator waveguide and electrode, a PdSe2 detector waveguide and electrode, and an optical waveguide connecting the two devices. The straight and curved waveguides are optimized using scanning parameter simulation to reduce light intensity loss.

[0011] Step 2: Fabrication of the integrated chip of thin-film lithium niobate modulator and PdSe2 detector Step 2-1: Using a silicon dioxide layer and a lithium niobate thin film sequentially arranged on a silicon substrate as a substrate, a chromium thin film is deposited on the lithium niobate thin film, and the mask pattern designed in Step 1 is prepared by using femtosecond laser direct writing technology to obtain a waveguide mask for an integrated chip composed of a modulator waveguide, a detector waveguide and a bent waveguide. Step 2-2: Polish and etch the substrate with the waveguide mask to transfer the pattern of the mask onto the lithium niobate film. Then, use a chromium etching solution to etch away the chromium mask on the surface of the substrate to obtain the waveguide structure of the integrated chip consisting of a modulator waveguide, a detector waveguide, and a bent waveguide. Steps 2-3: Metal coating is performed on the waveguide structure using magnetron sputtering, and then femtosecond laser is used to write on the metal mask to obtain an electrode mask with modulator and detector. Steps 2-4: Use an etching solution to etch the unprotected metal on the substrate surface of the electrode mask in sequence, and then use an acid and alkali solution to clean the substrate to obtain an integrated chip of lithium niobate modulator and PdSe2 detector. Steps 2-5: Polish the end faces of the integrated chip of lithium niobate modulator and PdSe2 detector using chemical mechanical polishing; Steps 2-6: The palladium diselenide substrate material that has been stripped multiple times is transferred to the detector electrode of the integrated chip using the PDMS dry transfer method, thereby obtaining an integrated chip consisting of a lithium niobate on-chip modulator, a PdSe2 photodetector, and an optical waveguide.

[0012] The lithium niobate film has a thickness of 500-5000 nm; the silicon dioxide layer has a thickness of 1-5 μm; the electrode is made of gold-chromium, with a gold layer thickness of 200 nm and a chromium layer thickness of 30 nm; and the PdSe2 material has a thickness of 20 nm to 200 nm.

[0013] The present invention will be further described below with reference to embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0014] Example 1 The fabrication steps of an integrated chip combining a lithium niobate on-chip modulator and a palladium diselenide photodetector are as follows: Step 1: Structural Design of Thin-Film Lithium Niobate Modulator Integrated with PdSe2 Detector See Figure 1 The thin-film lithium niobate modulator and detector integrated chip design consists of an on-chip lithium niobate modulator 1, a PdSe2 photodetector 2, and an optical waveguide 3. Its design includes: 1) An on-chip modulator for lithium niobate was designed using a Mach-Zehnder (MZ) interferometer configuration. The modulator structure was simulated using Lumerical software, and the thickness, spacing, and length of the modulator electrodes were optimized to achieve a theoretical bandwidth exceeding 10 GHz. Then, an on-chip detector structure was designed. To improve the evanescent wave coupling efficiency between the PdSe2 material and the laser within the optical waveguide, the thickness of the detector electrodes and the PdSe2 material were optimized. 2) To improve the separation and collection speed of photogenerated carriers in the detector, the electrode spacing and shape of the detector are optimized; 3) Design the optical waveguide connecting the two devices, including a straight waveguide and two bent waveguides 3, optimizing the bending radius (2mm) to minimize light intensity loss. Based on the above design, the design layout of the lithium niobate waveguide can be obtained, which includes: the waveguide and electrodes of the lithium niobate modulator 1, the waveguide and electrodes of the PdSe2 detector 2, and the straight and bent waveguides 3. Step 2: Fabrication of a thin-film lithium niobate modulator integrated with a PdSe2 detector 1) Take a lithium niobate substrate on an insulator, which mainly consists of three layers: the bottom layer is a 525 μm thick silicon substrate 6, the upper surface of which has a 4.7 μm silicon dioxide layer 5, and the upper surface of the silicon dioxide layer has a 500 nm thick thin film of lithium niobate 4; deposit a chromium film on the lithium niobate film, and use photolithography to prepare a mask pattern with a specific structure.

[0015] 2) The design layout of the integrated chip of lithium niobate modulator 1 and PdSe2 detector 2 is converted into a photolithographic layout, and a femtosecond laser is used to write on the chromium mask of the substrate to obtain a mask containing an integrated chip consisting of modulator waveguide, detector waveguide and bent waveguide.

[0016] 3) The substrate with the mask is polished and etched using chemical mechanical polishing to transfer the pattern of the mask onto the thin film lithium niobate. Then, the chromium mask on the surface of the substrate is etched away using a chromium etching solution to obtain a waveguide mask containing an integrated chip consisting of a modulator waveguide, a detector waveguide, and a bent waveguide.

[0017] 4) Metal coating is performed on the integrated chip waveguide by magnetron sputtering, and then femtosecond laser is used to write on the metal mask of the substrate to obtain an electrode mask containing an integrated chip consisting of modulator electrode 1 and detector electrode 8.

[0018] 5) Use an etching solution to etch away the unprotected metal on the substrate surface in sequence, and then use an acid or alkali solution to clean the substrate to obtain the electrode structure of the integrated chip consisting of modulator electrode 1 and detector electrode 8.

[0019] 6) Polish the end face of the lithium niobate modulator and detector integrated chip by chemical mechanical polishing.

[0020] 7) The palladium diselenide body material was peeled off multiple times using Scottish tape. Material 7 of appropriate size and thickness was selected and transferred to the detector electrode of the integrated chip by PDMS dry transfer method.

[0021] Thus, an integrated chip consisting of a lithium niobate on-chip modulator, a PdSe2 photodetector, and an optical waveguide was fabricated. The thickness of the lithium niobate thin film in the integrated chip is selected as 500-5000 nm; the thickness of the silicon dioxide layer on the substrate is selected as 1-5 μm; the thickness of the silicon substrate can be arbitrarily selected according to requirements; the thickness of the gold electrode is selected as 200 nm; and the thickness of the palladium diselenide material is selected as 5 nm-200 nm.

[0022] See Figure 1 A thin-film lithium niobate modulator and PdSe2 detector integrated chip implemented by the above method, comprising a lithium niobate electro-optic intensity modulator 1, a PdSe2 on-chip photodetector 2, a bent waveguide 3, a lithium niobate thin film 4, a silicon dioxide substrate 5, and a silicon substrate 6.

[0023] Step 3: Performance testing of the integration of thin-film lithium niobate modulator with PdSe2 detector A 1550 nm light source was connected to an intensity amplifier and then coupled to the incident end of a lithium niobate photonic chip via a fiber optic conical lens. One port of a vector network analyzer was connected to an RF cable and then applied to the modulator electrode via a high-frequency GSG probe. The other port of the vector network analyzer was connected to an RF cable and then applied to the detector electrode via a high-frequency GSG probe. A 50-ohm load was connected to the modulator electrode via a high-frequency GSG probe. Using this method, an integrated chip combining a thin-film lithium niobate modulator and a PdSe2 detector was fabricated, and the integrated bandwidth exceeded 2 GHz in RF signal transmission experiments.

[0024] See Figure 2 A lithium niobate on-chip photodetector 2 based on palladium diselenide material, including detector electrode 8 and palladium diselenide material 7.

[0025] See Figure 3 The curves showing the change in detector responsivity with light intensity under different applied bias voltages show that the responsivity can exceed 0.3 A / W.

[0026] See Figure 4 When a vector network analyzer applies a radio frequency (RF) signal to the lithium niobate electro-optic intensity modulator, the light intensity within the lithium niobate waveguide changes with the RF signal, and the palladium diselenide photodetector can detect this signal change at high speed. This integrated chip has a 3dB bandwidth exceeding 2GHz.

[0027] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating an integrated chip of an on-chip modulator and a palladium diselenide photodetector, characterized in that, The application discloses a method for preparing an integrated chip of an on-chip modulator and a two-dimensional material photoelectric detector on a lithium niobate substrate, realizes a modulation process of converting an electrical signal into an optical signal and a detection process of converting an optical signal into an electrical signal, and specifically comprises the following steps. Step 1: structure design of an integrated chip of a thin-film lithium niobate modulator and a PdSe2 detector Step 1-1: a lithium niobate on-chip modulator is designed in a Mach-Zehnder interferometer configuration, a lumerical software is used to simulate the modulator structure, the electrode thickness, spacing and length of the modulator are simulated and optimized by scanning parameters, and the theoretical bandwidth of the modulator is more than 10 GHz; Step 1-2: the structure of the on-chip detector is designed, the electrode spacing and shape of the detector are optimized by scanning parameter simulation, and the carrier transport efficiency of PdSe2 material is improved; Step 1-3: straight waveguides and curved waveguides connecting the two devices are designed, and an integrated chip design layout including a lithium niobate modulator waveguide and electrodes, a PdSe2 detector waveguide and electrodes and optical waveguides connecting the two devices is obtained; the straight waveguides and curved waveguides are optimized by scanning parameter simulation to reduce optical intensity loss; Step 2: preparation of an integrated chip of a thin-film lithium niobate modulator and a PdSe2 detector Step 2-1: a silicon substrate is used as a substrate, a silicon dioxide layer and a lithium niobate thin film are sequentially arranged on the substrate, a chromium thin film is deposited on the lithium niobate thin film, a mask pattern of the structure designed in step 1 is prepared by using a femtosecond laser direct writing technology, and a waveguide mask plate of the integrated chip composed of a modulator waveguide, a detector waveguide and a curved waveguide is obtained; Step 2-2: the substrate provided with the waveguide mask plate is polished and etched, the pattern of the mask plate is transferred to the lithium niobate thin film, then a chromium etching solution is used to etch the chromium mask on the surface of the substrate, and a waveguide structure of the integrated chip composed of a modulator waveguide, a detector waveguide and a curved waveguide is obtained; Step 2-3: metal film plating is performed on the waveguide structure by using a magnetron sputtering method, then femtosecond laser is used to write on the metal mask, and an electrode mask plate with a modulator and a detector is obtained; Step 2-4: the electrode mask plate is etched with an etching solution to sequentially etch the unprotected metal on the surface of the substrate, then the substrate is cleaned by using an acid-alkali solution, and an integrated chip of a lithium niobate modulator and a PdSe2 detector is obtained; Step 2-5: chemical mechanical grinding is used to polish the end surface of the integrated chip of the lithium niobate modulator and the PdSe2 detector; Step 2-6: a PDMS dry transfer method is used to transfer a multiple times exfoliated PdSe2 material to the detector electrode of the integrated chip, and the integrated chip composed of a lithium niobate on-chip modulator, a PdSe2 photoelectric detector and an optical waveguide is prepared.

2. The method of claim 1, wherein the method further comprises: The thickness of the lithium niobate thin film is 500-5000 nm; the thickness of the silicon dioxide layer is 1-5 um.

3. The method of claim 1, wherein the method further comprises: The material of the electrode is gold-chromium, the thickness of the gold layer is 200 nm, the thickness of the chromium layer is 30 nm, and the thickness of the PdSe2 material is 20 nm-200 nm.

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