Thermo-optical phase shifter based on indium tin oxide thin film, preparation method and application of thermo-optical phase shifter

Abstract

The invention discloses a thermo-optical phase shifter based on an indium tin oxide thin film, a preparation method and application thereof, and belongs to the field of photonics devices. Comprising the following steps: patterning the surface of a substrate including a substrate layer and a top silicon layer; performing graphical photoetching on the top silicon layer, etching to generate a groove, and forming a silicon waveguide layer; the isolation layer covers the silicon waveguide layer; the indium tin oxide thin film covers the isolation layer; the metal electrodes are connected with the two sides of the indium tin oxide thin film through the adhesion layers; the protective layer is located between the two metal electrodes and covers the surface of the indium tin oxide thin film. When the device is applied to MZI, heat generated by the indium tin oxide thin film is transmitted to the silicon waveguide, and phase difference is accumulated on an interference arm to achieve optical signal phase modulation. The interference state of the MZI is dynamically switched, and optical power redistribution of the two output ports is achieved. According to the thermo-optical phase shifter, the electro-thermal-optical synergistic characteristic of the ITO thin film is combined, the core advantages of high response rate, high energy efficiency, low insertion loss and low thermal crosstalk are achieved, meanwhile, the manufacturing process of the thermo-optical phase shifter is compatible with the standard CMOS process, and the production cost is low.

Description

Technical Field

[0001] The present invention belongs to the field of integrated photonics device manufacturing and relates to a thermo-optical phase shifter based on an indium tin oxide film, a preparation method and an application thereof. Background Art

[0002] Optical phase shifters are fundamental building blocks for optical interferometers, optical modulators, and reconfigurable photonic integrated links. By precisely adjusting the phase of optical signals, these devices enable dynamic control of optical transmission paths and are a key technology for dynamically reconfigurable optical routers. For these systems, phase shifters with high response speed, compact control unit size, and low optical loss are crucial for improving the scalability and performance of optical networks. Currently, existing thermo-optical phase shifter designs primarily utilize microheaters made of metals (such as TiN) or metal composites. To reduce optical losses caused by metal absorption, a silicon dioxide (SiO2) isolation layer thicker than 1μm is typically introduced between the heater and the optical waveguide. While this design effectively reduces optical losses, it also significantly reduces heat transfer efficiency, extending response times to over 10μs, increasing modulation power consumption to as high as 200mW / π phase change, and resulting in extremely inefficient thermal management.

[0003] These challenges limit the energy efficiency and response speed of existing phase shifters, making them difficult to meet the requirements of high-performance on-chip optical phase shifters. Therefore, developing a new phase shifter design that can provide higher thermo-optical efficiency, faster response speed and lower power consumption is of great significance for the development of high-speed dynamically reconfigurable cascaded optical networks and high-speed data center optical interconnects. Summary of the Invention

[0004] In response to the above-mentioned deficiencies or improvements in the prior art, the present invention provides a thermo-optical phase shifter based on indium tin oxide thin film and a method for preparing the same, thereby resolving the technical problems of low response rate, high power consumption, and high thermal crosstalk in the prior art. The thermo-optical phase shifter of the present invention combines the electro-thermal-optical synergistic properties of indium tin oxide thin film to achieve the core advantages of high response rate, high energy efficiency, low insertion loss, and low thermal crosstalk. At the same time, its manufacturing process is compatible with standard CMOS processes and has low production costs. This combination of properties is of great significance to the development of high-speed, dynamically reconfigurable cascaded optical networks and high-speed data center optical interconnects.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A thermo-optical phase shifter based on an indium tin oxide film, comprising a protective layer 106, a metal electrode 105, an adhesion layer 104, an indium tin oxide film 103, an isolation layer 102, a silicon waveguide layer 101, and a substrate 100 stacked in sequence. Specifically:

[0007] The substrate 100 is an SOI substrate, the surface of which is patterned. The substrate 100 includes a substrate layer and a top silicon layer from bottom to top.

[0008] The top silicon layer is patterned by photolithography and etched to produce grooves to form a silicon waveguide layer 101. An oxide layer is deposited on the entire surface of the waveguide structure to cover it. The silicon waveguide structure is exposed by local wet etching to obtain the silicon waveguide layer 101.

[0009] The isolation layer 102 completely covers the silicon waveguide layer 101;

[0010] The indium tin oxide film 103 completely covers the isolation layer 102;

[0011] There are two metal electrodes 105 , both of which are long strip structures and are connected to both sides of the ITO film 103 via the adhesive layer 104 . L1 represents the distance between the two metal electrodes 105 , and the distance range is 5-20 μm.

[0012] The protection layer 106 is located between the two metal electrodes 105 and completely covers the surface of the ITO film 103 .

[0013] Furthermore, a top silicon layer is formed on the substrate 100 by a bond-strip method. The top silicon layer is patterned by photolithography and etched to form grooves and a silicon waveguide layer 101. The grooves are located on both sides of the silicon waveguide layer 101 and are used to define the boundaries of the silicon waveguide layer 101. Wider waveguides require wider trenches to provide sufficient isolation and achieve lower transmission loss. The trench structure has a width of 1 μm to 5 μm, a trench depth of 40 nm to 220 nm, and a width of the silicon waveguide layer 101 of 500 nm to 3 μm.

[0014] Furthermore, an isolation layer 102 is deposited by magnetron sputtering. The isolation layer 102 is covered on the silicon waveguide layer 101 and the groove surface and the surrounding area by patterned photolithography technology. The isolation layer material 102 can be Al2O3, Si3N4 or SiO2, and the film thickness is 10nm-200nm.

[0015] Furthermore, an indium tin oxide film 103 is deposited by magnetron sputtering. The indium tin oxide film 103 is covered on the surface of the isolation layer 102 by patterned photolithography technology and is tightly connected thereto. The thickness of the indium tin oxide film 103 is 10 nm to 300 nm.

[0016] Furthermore, an adhesion layer 104 is deposited by magnetron sputtering. This adhesion layer is deposited using patterned photolithography techniques only on the edges of the surface of the indium tin oxide film 103, forming a connection therewith. L1 represents the distance between the two adhesion layers 104 and the silicon waveguide layer 101, which ranges from 5 to 20 μm. Adhesion layer 104 can be made of Ti or TiN and has a thickness of 10 nm.

[0017] Furthermore, metal electrodes 105 are deposited by magnetron sputtering. These metal electrodes 105 are deposited using patterned photolithography techniques to cover only the surface of the adhesion layer 104. The upper surface of the adhesion layer 104 is flush with the lower surface of the metal electrodes 105. L1 represents the distance between the two metal electrodes 105, which ranges from 5 to 20 μm. The metal electrodes 105 can be made of Au, Cu, Pt, or Ag, and have a thickness of 20 nm to 200 nm.

[0018] Furthermore, a protective layer 106 is deposited by magnetron sputtering. The protective layer 106 covers the surface of the indium tin oxide film 103 by patterned photolithography technology, and partially covers the surface of the metal electrode 105 located on both sides of the indium tin oxide film 103. The material of the protective layer 106 can be Al2O3, Si3N4 or SiO2, and its thickness is between 20nm and 200nm.

[0019] The design principle of this invention is as follows: During the modulation process of the optical phase shifter, an electrical pulse signal is applied to the indium tin oxide (ITO) thin film to generate localized Joule heating. The heat is efficiently transferred vertically to the underlying silicon waveguide through the ultra-thin aluminum oxide isolation layer. The refractive index of the waveguide changes due to the temperature increase, accumulating phase differences in the interferometer arms, ultimately achieving phase modulation of the optical signal. This phase change dynamically switches the interference state of the Mach-Zehnder interferometer (MZI), achieving optical power redistribution between the two output ports.

[0020] A method for preparing a thermo-optical phase shifter based on an indium tin oxide thin film comprises the following steps:

[0021] Step (1) forms the top silicon layer on the surface of the substrate 100 by bonding and peeling, and performs patterning, photolithography, and etching on the top silicon layer to form a groove and a silicon waveguide layer 101, wherein the groove is located on both sides of the silicon waveguide layer 101; the groove structure width is 1 μm-5 μm, the groove depth is 40 nm-220 nm, and the silicon waveguide width is 500 nm-3 μm.

[0022] Step (2), depositing an isolation layer 102 with a thickness of 10 nm to 200 nm on the silicon waveguide layer 101;

[0023] Step (3), depositing a 10nm-400nm indium tin oxide thin film 103 on the isolation layer 102;

[0024] In step (4), a 10 nm thick adhesion layer 104 is deposited on the ITO film 103. The adhesion layer 104 is deposited on the edges of both sides of the surface of the ITO film 102 and connected thereto. L1 represents the distance between the two adhesion layers 104 and the silicon waveguide layer 101, and the distance range is 5-20 μm.

[0025] In step (5), a metal electrode 105 having a thickness of 20 nm to 200 nm is deposited on the adhesion layer 104. The metal electrode 105 covers the surface of the adhesion layer 104, and the upper surface of the adhesion layer 104 is flush with the lower surface of the metal electrode 105. L1 represents the distance between the two metal electrodes 105 and the silicon waveguide layer 101, and the distance range is 5-20 μm.

[0026] Step (6): depositing a protective layer 106 with a thickness of 20-200 nm on the ITO film 103 .

[0027] The protective layer 106 completely covers the central area of the surface of the ITO film 103 through patterned photolithography, and also partially covers the metal electrodes 105 located on both sides of the protective layer 106 .

[0028] Furthermore, the etching in step (1) is electron beam lithography or plasma etching; the deposition in steps (2) to (6) is chemical vapor deposition, physical vapor deposition, electron beam evaporation coating, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering or radio frequency magnetron sputtering, and the deposition methods in each step may be the same or different.

[0029] An application of a thermo-optical phase shifter based on an indium tin oxide film is disclosed, and a Mach-Zehnder interferometer (MZI) structure is fabricated based on the thermo-optical phase shifter. The Mach-Zehnder interferometer structure includes a 1×2 beam splitter 108, an interferometer arm 109, a retaining arm 110, a phase shifter unit 111, a 2×2 beam splitter 112, a first output port 113, and a second output port 114. The MZI modulation unit is composed of the interferometer arm 109, the retaining arm 110, and the phase shifter unit 111 integrated in the interferometer arm 109. Specifically:

[0030] An optical signal is input through the input waveguide 107, and the input end of the 1×2 beam splitter 108 is connected to the input waveguide 107. The 1×2 beam splitter 108 splits the optical signal into two paths according to a certain ratio, and connects them to the interference arm 109 and the holding arm 110 respectively. The interference arm 109 and the holding arm 110 are respectively connected to the first output port 113 and the second output port 114 through the 2×2 beam splitter 112.

[0031] By applying voltage to the metal electrodes 105 on both sides of the phase shifter unit 111, the indium tin oxide film 103 generates local Joule heating. The heat is efficiently transferred vertically to the underlying silicon waveguide layer 101 through the ultra-thin isolation layer 102. The refractive index of the waveguide changes due to the increase in temperature, thereby accumulating phase differences in the interferometer arms 109, ultimately achieving phase modulation of the optical signal.

[0032] The invention's innovative features include the use of an ultrathin isolation layer to achieve near-field thermal coupling between the ITO microheater and the waveguide, significantly reducing the thermal response time to less than 2 microseconds and increasing the modulation speed tenfold compared to conventional metal heaters. The high thermo-optical coefficient of ITO, in synergy with near-field heat conduction, significantly reduces modulation power consumption. This method not only improves modulation efficiency but also optimizes modulation energy efficiency and response rate, meeting the requirements for dynamic control of MHz-class array optical phase shifters and thus possessing significant application potential in high-speed optical communication systems.

[0033] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0034] (1) In the process of modulating the optical phase shifter, local Joule heating is generated by applying an electric pulse signal to the indium tin oxide (ITO) film. The heat is efficiently transferred vertically to the silicon waveguide below through the ultra-thin aluminum oxide isolation layer. The refractive index of the waveguide changes due to the temperature increase, thereby accumulating a phase difference in the interference arm, and ultimately achieving phase modulation of the optical signal. This phase change causes the interference state of the Mach-Zehnder interferometer (MZI) to switch dynamically, realizing the redistribution of optical power between the two output ports. The ultra-thin isolation layer is used to achieve near-field thermal coupling between the ITO microheater and the waveguide, significantly shortening the thermal response time to less than 2 microseconds, which is 10 times faster than the modulation speed of traditional metal heaters. The high thermo-optical coefficient of ITO is used in conjunction with near-field heat conduction to significantly reduce the modulation power consumption. This method not only improves the modulation efficiency, but also optimizes the modulation energy efficiency and response rate, meeting the dynamic control requirements of MHz-level array optical phase shifters, making the phase shifter have significant application potential in high-speed optical communication systems.

[0035] (2) Indium tin oxide (ITO) exhibits unique electro-thermal-optical synergistic properties due to its extremely high transparency in the communication band, magnetron sputtering deposition process that is fully compatible with standard CMOS processes, and good electrical conductivity: its high electrical conductivity and significant thermal resistivity ensure high electro-thermal conversion efficiency. The low heat capacity of the film itself and its direct deposition and integration as a microheater on the silicon waveguide, which is closely coupled with the light field to form an extremely short heat conduction path, ensure that heat can be quickly generated and transferred to the silicon waveguide area, achieving an ultra-fast thermal response speed of less than 2 microseconds. At the same time, its high transparency in the communication band enables it to be integrated as a top heater with low optical loss. In addition, the magnetron sputtering process can be precisely controlled to prepare highly conductive films with excellent uniformity and good crystal quality. These combined characteristics optimize the electro-thermal-optical synergistic properties of ITO, making it an ideal choice for realizing high-speed, high-energy-efficiency, and CMOS-compatible silicon-based thermo-optical phase shifters. This unique electro-thermal-optical synergistic property makes ITO film an ideal microheater material with fast response rate, high energy efficiency, and CMOS process compatibility.

[0036] In summary, the present invention's thermo-optical phase shifter based on ITO thin film leverages ITO's excellent electro-thermal-optical synergy, low loss characteristics, and efficient thermal management to achieve a high-response rate, high energy efficiency, and low-loss thermo-optical modulator. This has important implications for the development of high-speed, dynamically reconfigurable cascaded optical networks and high-speed data center optical interconnects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of a thermo-optical phase shifter based on an indium tin oxide film provided in Example 1 of the present invention;

[0038] Figure 2 This is a substrate diagram of a thermo-optical phase shifter based on an indium tin oxide thin film provided in Example 1 of the present invention, which has not been etched;

[0039] Figure 3 This is a top view of a thermo-optical phase shifter based on an indium tin oxide thin film after etching provided by Example 1 of the present invention;

[0040] Figure 4 is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide thin film after etching provided in Example 1 of the present invention;

[0041] Figure 5 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film provided in Example 1 of the present invention after an isolation layer is deposited;

[0042] Figure 6 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide thin film provided in Example 1 of the present invention after the indium tin oxide thin film is deposited;

[0043] Figure 7 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film provided in Example 1 of the present invention after an adhesion layer is deposited;

[0044] Figure 8 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film provided in Example 1 of the present invention after a metal electrode film is deposited;

[0045] Figure 9 Schematic diagram of a Mach-Zehnder interferometer (MZI) structure device prepared by a thermo-optical phase shifter based on an indium tin oxide thin film provided in Example 1 of the present invention;

[0046] Figure 10 The modulation voltage-splitting ratio curve is shown in Figure 1. In Example 1 of the present invention, a voltage signal is applied to the indium tin oxide thin film to generate Joule heating. This heat is efficiently transferred vertically to the underlying silicon waveguide via an ultra-thin aluminum oxide isolation layer. The temperature rise causes the waveguide's refractive index to change, accumulating phase differences in the interferometer arms and ultimately achieving phase modulation of the optical signal. This phase change dynamically switches the interference state of the Mach-Zehnder interferometer (MZI), redistributing the optical power between the two output ports.

[0047] Figure 11 This is the phase shift and temperature curve corresponding to the modulation voltage. Example 1 of the present invention provides a method for generating Joule heating by applying a voltage signal to an indium tin oxide thin film. This heat is efficiently transferred vertically to the underlying silicon waveguide via an ultra-thin aluminum oxide isolation layer. As the voltage increases, the right axis shows the trend of increasing waveguide temperature, while the left axis shows the corresponding change in optical signal phase shift.

[0048] Figure 12 2 is a diagram of the modulation response rate of an optical signal. In the MZI sample including a thermo-optical phase shifter provided in Example 1 of the present invention, a square wave voltage signal is applied to the indium tin oxide film-assisted optical phase shifter using a signal generator. The optical signal output from the first output port 113 enters a photodetector and is converted into an electrical signal. The modulated waveform of the electrical signal is recorded using an oscilloscope to obtain the response rate of the thermo-optical phase shifter.

[0049] Figure 13 This is a top view of a thermo-optical phase shifter based on an indium tin oxide thin film after etching provided by Example 2 of the present invention;

[0050] Figure 14 is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide thin film after etching provided in Example 2 of the present invention;

[0051] Figure 15 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film after an isolation layer is deposited, provided in Example 2 of the present invention;

[0052] Figure 16 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide thin film after deposition of the indium tin oxide thin film, provided in Example 2 of the present invention;

[0053] Figure 17 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film after an adhesion layer is deposited, provided in Example 2 of the present invention;

[0054] Figure 18 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film after a metal electrode film is deposited, provided in Example 2 of the present invention;

[0055] Figure 19 This is a cross-sectional view of a thermo-optical phase shifter based on an indium tin oxide film after a protective layer is deposited, provided in Example 2 of the present invention;

[0056] Figure 20 Schematic diagram of a microring resonator (MRR) structure device prepared by a thermo-optical phase shifter based on an indium tin oxide thin film provided in Example 2 of the present invention;

[0057] Figure 21 This is a graph showing the relationship between the optical spectrum curve and the applied voltage of a microring resonator (MRR) structure device prepared by a thermo-optical phase shifter based on an indium tin oxide thin film provided in Example 2 of the present invention;

[0058] In the figure: 100 substrate; 101 silicon waveguide; 102 isolation layer; 103 indium tin oxide film; 104 adhesion layer; 105 metal electrode; 106 protective layer; 107 input waveguide; 108 1×2 beam splitter; 109 interference arm; 110 holding arm; 111 phase shifter unit, which is a thermo-optical phase shifter based on indium tin oxide film designed by the present invention; 112 2×2 beam splitter; 113 first output port; 114 second output port; 115 microring input waveguide; 116 microring output waveguide; 117 ring waveguide. DETAILED DESCRIPTION

[0059] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0060] This modulator achieves optical signal modulation based on the thermo-optic effect of silicon and the principle of interferometric phase control. Its core principle is to apply an electrical pulse signal to an indium tin oxide (ITO) thin film to generate localized Joule heating. This heat is efficiently transferred vertically to the underlying silicon waveguide via an ultra-thin aluminum oxide isolation layer. The temperature rise causes the waveguide's refractive index to change, accumulating phase differences in the interferometer arms and ultimately achieving optical signal phase modulation. This phase change dynamically switches the interference state of the Mach-Zehnder interferometer (MZI), redistributing the optical power between the two output ports.

[0061] like Figure 1 The figure shows a thermo-optical phase shifter based on an indium tin oxide film according to embodiment 1 of the present invention, comprising a protective layer 106, a metal electrode 105, an adhesion layer 104, an indium tin oxide film 103, an isolation layer 102, an etched silicon waveguide layer 101, and a substrate 100. The width of the waveguide structure is 500nm-3μm, and the etching depth is 40nm-220nm. The thickness of the isolation layer 102 is 10nm-200nm. The thickness of the indium tin oxide film 103 is 10nm-400nm. The thickness of the protective layer 106 is 20-200nm, and the protective layer 106 is SiO2, Al2O3, or SiN x The thickness of the metal electrode 105 is 20 nm to 200 nm, and the metal electrode 105 is a Ag, Cu, Pt or Au thin film. The thickness of the adhesion layer 104 is 10 nm, and the adhesion layer 104 is a Ti or TiN thin film.

[0062] Figure 2-Figure 9 This is a preparation process of a thermo-optical phase shifter based on an indium tin oxide thin film provided in Example 1 of the present invention.

[0063] Figure 2 is a substrate image without etching; patterning photolithography and etching are performed on the surface of the substrate 100 to produce grooves to form the silicon waveguide layer 101, as shown in FIG. Figure 3 The top view of the waveguide structure after etching is shown in FIG. Figure 4 The cross-sectional view of the waveguide structure after etching is shown in FIG. Figure 5 As shown, an isolation layer 102 with a thickness of 10nm-200nm is deposited on top of the silicon waveguide layer 101 structure; Figure 6 As shown, a 10nm-400nm indium tin oxide film 103 is deposited on the isolation layer 102; Figure 7 As shown in FIG, a 10 nm thick adhesion layer 104 is deposited on top of the ITO film 103. Figure 8As shown, a 20-200 nm metal electrode 105 is deposited on the adhesion layer 104. The etching is electron beam lithography or ion coupled plasma etching, and the deposition is chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering or radio frequency magnetron sputtering.

[0064] Figure 9 The structure disclosed in this disclosure is applied in the field of integrated photonic devices. A silicon-based MZI thermo-optical phase shifter assisted by an indium tin oxide film is designed. The structure of the device is as follows: Figure 9 As shown, the MZI modulation unit includes an isolation layer 102, an indium tin oxide film 103, a protective layer 106, an adhesion layer 104, a metal electrode 105, and a protective layer 106. An input waveguide 107 is used to input an optical signal. The input end of a 1×2 beam splitter 108 is connected to the input waveguide 107. The 1×2 beam splitter 108 is used to split the optical signal into two paths according to a certain ratio. The MZI modulation unit includes an interferometer arm 109, a retaining arm 110, and a phase shifter unit 111 integrated into the interferometer arm 109 and connected to the 1×2 beam splitter 108. The phase shifter unit is deposited simultaneously on the interferometer arm 109 and the retaining arm 110 in the following order: first, the isolation layer 102 and the indium tin oxide film 103 are deposited, then the adhesion layer 104 and the metal electrode 105 are deposited to reduce contact resistance, and finally, the protective layer 106 is deposited. The phase shifter unit in arm 110 is used to balance losses.

[0065] According to Example 1 of the present disclosure, an electric pulse applied through the metal electrode 105 is transmitted to the microheater indium tin oxide film 103, generating localized Joule heating. This heat is efficiently transferred vertically to the underlying silicon waveguide layer 101 via the ultra-thin aluminum oxide isolation layer 102. The waveguide's refractive index changes due to the temperature increase, accumulating a phase difference in the interferometer arm 109, ultimately achieving phase modulation of the optical signal. This phase change dynamically switches the interference state of the Mach-Zehnder interferometer (MZI), redistributing the optical power between the first output port 113 and the second output port 114.

[0066] According to embodiment 1 of the present disclosure, the modulated optical signal is transmitted to the 2×2 beam splitter 112 through the interference arm 109, and interferes with the initial optical signal from the holding arm 110. The interfered optical signal is split into two beams by the 2×2 beam splitter 112 and then passes through the first output port 113 and the second output port 114.

[0067] Figure 10This is a relationship diagram between the electric pulse applied to the indium tin oxide film and the splitting ratio of the two ports of the MZI provided in Example 1 of the present invention. The optical signal modulation is realized based on the thermo-optical effect and the interference phase control principle. The electric pulse signal is applied to the indium tin oxide (ITO) film to generate local Joule heating. The heat is efficiently transferred vertically to the silicon waveguide below through the ultra-thin aluminum oxide isolation layer. The refractive index of the waveguide changes due to the temperature increase, thereby accumulating the phase difference in the interference arm, and finally realizing the phase modulation of the optical signal. This phase change causes the interference state of the Mach-Zehnder interferometer (MZI) to switch dynamically, realizing the optical power redistribution of the two output ports. Using Figure 10 The MZI device shown was used to test the prepared optical phase shifter in the 1550 nm band, showing the power changes of the two channels corresponding to different voltages. The phase modulation efficiency of the thermo-optical phase shifter was as high as 3V / π, and the corresponding energy consumption was as low as 30mW / π, showing the advantages of high energy-efficient thermal management and low power consumption.

[0068] Figure 11 This is a diagram showing the modulation effect of the optical phase shifter provided in Example 1 of the present invention in the MZI sample. By applying electrical pulse signals of different amplitudes, the optical phase shifter produces different phase differences. The diagram shows the correspondence between the amplitude of the electrical pulse signal and the modulation amplitude of the thermo-optical phase shifter, as well as the corresponding temperature change of the silicon waveguide.

[0069] Figure 12 This is a graph showing the modulation response rate of an optical signal. Using the MZI sample containing a thermo-optical phase shifter provided in Example 1 of the present invention, a square wave voltage signal was applied to the indium tin oxide thin film-assisted optical phase shifter via a signal generator. The optical signal output from the first output port 113 was converted into an electrical signal after entering a photodetector. The modulated waveform of the electrical signal was recorded using an oscilloscope to obtain the response rate of the thermo-optical phase shifter. During the on and off cycles of the applied voltage signal, the time required for the phase change to reach its maximum value was less than 2 microseconds, a tenfold increase in the modulation speed of a conventional metal heater, demonstrating the high response rate of the optical phase shifter of the present invention.

[0070] Figures 13-19 Embodiment 2 of the present invention provides a preparation process of a thermo-optical phase shifter based on an indium tin oxide film.

[0071] like Figure 13 The figure shows a top view of the substrate after etching in accordance with the second embodiment of the present invention. Patterned photolithography and etching are performed on the surface of the substrate 100 to form grooves to form the silicon waveguide layer 101. Figure 14 The figure shows the cross-section of the waveguide structure after etching; Figure 15 As shown, an isolation layer 102 with a thickness of 10nm-200nm is deposited on the silicon waveguide layer 101 structure; Figure 16As shown, a 10nm-400nm indium tin oxide film 103 is deposited on the isolation layer 102; Figure 17 As shown in FIG, a 10 nm thick adhesion layer 104 is deposited on both side edges of the ITO film 103. Figure 18 As shown, a metal electrode 105 with a thickness of 20-200 nm is deposited on the adhesion layer 104, and the upper surface of the adhesion layer is flush with the lower surface of the metal electrode. Figure 19 As shown, a 20-200 nm thick protective layer 106 is deposited on top of the indium tin oxide film 103, completely covering the indium tin oxide film 103 and partially covering the metal electrode 105. The etching is performed by electron beam lithography or ion-coupled plasma etching, and the deposition is performed by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering.

[0072] like Figure 20 The figure shows a schematic diagram of a microring resonator (MRR) structure device prepared by a thermo-optical phase shifter based on an indium tin oxide film according to Example 2 of the present invention. The MRR structure device is characterized in that the indium tin oxide film 103 covers the entire ring waveguide 117 to provide sufficient phase shift and improve the phase shifting capability of the phase shifter.

[0073] like Figure 21 The figure shows the relationship between the spectral curve of a microring resonator (MRR) structure device prepared by a thermo-optical phase shifter based on an indium tin oxide film provided in Example 2 of the present invention and the voltage applied to the metal electrode 105. As the applied voltage increases, the resonance peak of the microring resonator moves toward a longer wavelength.

[0074] Example 1

[0075] like Figure 9 The figure shows the Mach-Zehnder interferometer (MZI) structure fabricated based on the thermo-optical phase shifter of indium tin oxide thin film. Figures 1 to 8 The present invention provides a method for preparing a thermo-optical phase shifter based on an indium tin oxide film, the method comprising the steps of:

[0076] like Figure 2 The figure shows a substrate that has not been etched. Before etching, the substrate should be cleaned with deionized water to ensure that the substrate is clean and that the subsequent etching and deposition steps are not interfered with by impurities.

[0077] like Figure 3 FIG. 1 shows a top view of the substrate after etching. The specific waveguide etching steps include: forming a patterned substrate by electron beam lithography, etching a waveguide structure 101 on the substrate, and etching by dry etching. The waveguide width is 1 μm and the etching depth is 80 nm.

[0078] like Figure 4 , which is a cross-sectional view of the waveguide after etching. The portion between the two grooves is the etched waveguide 101 structure. The etched silicon waveguide layer 101 structure is the basic unit in the field of integrated photonics and serves as a medium for transmitting light waves.

[0079] like Figure 5 FIG. 1 is a cross-sectional view of depositing an isolation layer 102 on a waveguide. The specific steps include: first, forming a deposition area on the silicon waveguide layer 101 structure by patterned photolithography, and then depositing a 200 nm thick Al2O3 film as the isolation layer 102 on the waveguide by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0080] The isolation layer 102 is located above the etched waveguide structure 101 and is separated from the indium tin oxide film 103 to be deposited. The purpose of the isolation layer 102 is to reduce the contact distance between the indium tin oxide film 103 and the waveguide structure 101, thereby reducing the loss of the thermo-optical phase shifter based on the indium tin oxide film.

[0081] like Figure 6 FIG. 1 is a cross-sectional view of depositing an indium tin oxide thin film 103 on the isolation layer 102. The specific steps include: first, forming an area to be deposited on the isolation layer 102 by patterned photolithography, and then depositing a 270 nm thick indium tin oxide thin film 103 as a microheater on the isolation layer 102 by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0082] The indium tin oxide film 103 is the most critical structure of the indium tin oxide film-based thermo-optical phase shifter and also the functional structure of the indium tin oxide film-based thermo-optical phase shifter. By subsequently depositing a metal electrode 105, the indium tin oxide film 103 is energized, generating Joule heat. This heat conduction changes the temperature of the waveguide structure 101, thereby changing the refractive index of the waveguide structure 101 according to the thermo-optical effect, thereby performing modulation.

[0083] After the deposition of the indium tin oxide film 103 is completed, the device is usually subjected to high-temperature annealing to reduce the contact resistance of the indium tin oxide film 103;

[0084] like Figure 7FIG. 1 is a cross-sectional view of depositing an adhesion layer 104 on an indium tin oxide film 103. The specific steps include: first, forming an area to be deposited on the indium tin oxide film 103 by patterned photolithography, and then depositing a 10 nm thick layer of Ti as the adhesion layer 104 on both sides above the microheater by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0085] The adhesion layer 104 is an important part connecting the metal electrode 105 and the indium tin oxide film 103, ensuring that the metal electrode 105 is not easy to fall off after deposition, which is of great significance for the realization of the device function.

[0086] like Figure 8 , which is a cross-sectional view of depositing a metal electrode 105 on the adhesion layer 104. The specific steps include: first, forming a region to be deposited on the adhesion layer 104 by patterned photolithography, and then depositing a 100 nm thick Au layer as the metal electrode 105 on the adhesion layer by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0087] The metal electrodes 105 are located on both sides of the ITO film 103 and serve as direct contact layers for applied voltage. The deposition of the metal electrodes 105 can effectively reduce the contact resistance of the ITO film-based thermo-optical phase shifter.

[0088] like Figure 1 FIG. 1 is a cross-sectional view of depositing a protective layer 106 on the indium tin oxide film 103. The specific steps include: first, forming an area to be deposited on the indium tin oxide film 103 by patterned photolithography, and then depositing a 200 nm thick Al2O3 layer as the protective layer 106 on the microheater by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0089] The protective layer 106 is located above the ITO film 103 and is mainly used to isolate the ITO film 103 from the air and prevent the ITO film 103 from being oxidized when generating Joule heat, thereby reducing device performance.

[0090] like Figure 9 As shown in FIG, the structure of the Mach-Zehnder interferometer (MZI) prepared by the thermo-optical phase shifter based on the indium tin oxide film is successfully prepared after the above manufacturing steps. The structure of the device is as follows Figure 9As shown, it includes an isolation layer 102, an indium tin oxide film 103, a protective layer 106, an adhesion layer 104, a metal electrode 105, and a protective layer 106. An input waveguide 107 is used to input an optical signal. The input end of a 1×2 beam splitter 108 is connected to the input waveguide 107. The 1×2 beam splitter 108 is used to split the optical signal into two paths according to a certain ratio. The MZI modulation unit includes an interference arm 109, a holding arm 110, and a phase shifter unit 111 integrated in the interference arm 109 and connected to the 1×2 beam splitter 108.

[0091] The specific device implementation method is to Figure 9 When voltage is applied to the metal electrodes 105 on both sides, the indium tin oxide film 103 generates local Joule heating. The heat is efficiently transferred vertically to the silicon waveguide below through the ultra-thin aluminum oxide isolation layer. The refractive index of the waveguide changes due to the increase in temperature, thereby accumulating phase difference in the interferometer arm 109, ultimately achieving phase modulation of the optical signal.

[0092] Figure 10 The embodiment 1 provides Figure 9 The MZI device shown in the figure shows the test results of the optical phase shifter prepared in the 1550 nm band, which shows the power changes of the two channels corresponding to different voltages. The phase modulation efficiency of the thermo-optical phase shifter is as high as 3V / π, and the corresponding energy consumption is as low as 30mW / π, showing the advantages of high energy-efficient thermal management and low power consumption.

[0093] Figure 11 Example 1 provides Figure 9 The MZI sample modulation effect diagram shown in the figure causes the optical phase shifter to produce different phase differences by applying electrical pulse signals of different amplitudes. It shows the corresponding relationship between the amplitude of the electrical pulse signal and the modulation amplitude of the thermo-optical phase shifter, as well as the corresponding silicon waveguide temperature change.

[0094] Figure 12 Example 1 provides Figure 9 The figure shows the modulation response rate of the optical signal of the MZI sample. A signal generator applies a square wave voltage signal to the ITO thin film-assisted optical phase shifter. The optical signal output from the first output port 113 enters a photodetector and is converted into an electrical signal. The modulated waveform of the electrical signal is recorded on an oscilloscope to obtain the response rate of the thermo-optical phase shifter. During the on and off process of the applied voltage signal, the time required for the phase change to reach its maximum value is less than 2 microseconds, which is 10 times faster than the modulation speed of a traditional metal heater, demonstrating the high response rate of the optical phase shifter of the present invention.

[0095] Example 2

[0096] like Figure 20 The figure shows a microring resonator (MRR) structure device made of a thermo-optical phase shifter based on indium tin oxide thin film. Figures 13 to 19 The present invention provides a method for preparing a thermo-optical phase shifter based on an indium tin oxide film, the method comprising the steps of:

[0097] like Figure 13 FIG. 1 shows a top view of the substrate after etching. The specific waveguide etching steps include: forming a patterned substrate by electron beam lithography, etching a silicon waveguide layer 101 structure on the substrate using a dry etching method. The waveguide width is 1 μm and the etching depth is 80 nm.

[0098] like Figure 14 , which is a cross-sectional view of the waveguide after etching, and the groove part is the etched structure;

[0099] like Figure 15 , which is a cross-sectional view of depositing an isolation layer 102 on a waveguide, specifically comprises the following steps: first, forming an area to be deposited on the silicon waveguide structure 101 by patterned photolithography, and then depositing a 10 nm thick Al2O3 thin film as the isolation layer 102 on the waveguide by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0100] The isolation layer 102 is located above the etched silicon waveguide layer 101 structure and is separated from the indium tin oxide film 103 to be deposited. The purpose of the isolation layer 102 is to reduce the contact distance between the indium tin oxide film 103 and the silicon waveguide layer 101 structure, thereby reducing the loss of the thermo-optical phase shifter based on the indium tin oxide film.

[0101] like Figure 16 FIG. 1 is a cross-sectional view of depositing an indium tin oxide film 103 on the isolation layer 102. The specific steps include: first, patterning photolithography is used to form an area to be deposited above the isolation layer 102. The photolithographic deposition area needs to cover and surround the entire micro-ring structure. Then, a 200 nm thick indium tin oxide film 103 is deposited on the isolation layer as a micro-heater by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering.

[0102] The ITO film 103 is the most critical structure of the ITO-based thermo-optical phase shifter and also the functional structure of the ITO-based thermo-optical phase shifter. By subsequently depositing an adhesion layer 104 and a metal electrode 105, the ITO film 103 is energized, generating Joule heat. This heat conduction changes the temperature of the silicon waveguide layer 101, thereby changing the refractive index of the silicon waveguide layer 101 through the thermo-optical effect, thus achieving modulation.

[0103] After the deposition of the indium tin oxide film 103 is completed, the device is usually subjected to high-temperature annealing to reduce the contact resistance of the indium tin oxide film 103;

[0104] like Figure 17 FIG. 1 is a cross-sectional view of depositing an adhesion layer 104 on an indium tin oxide film 103. The specific steps include: first, patterning photolithography is used to form the deposition area at the edge positions on both sides of the indium tin oxide film 103; then, a 10 nm thick Ti layer is deposited on both sides of the microheater as the adhesion layer 104 by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0105] The adhesion layer 104 is an important part connecting the metal electrode 105 and the indium tin oxide film 103, ensuring that the metal electrode 105 is not easy to fall off after deposition, which is of great significance for the realization of the device function.

[0106] like Figure 18 , which is a cross-sectional view of depositing a metal electrode 105 on the adhesion layer 104. The specific steps include: first, forming a region to be deposited on the adhesion layer 104 by patterned photolithography, and then depositing a 100 nm thick Au layer as the metal electrode 105 on the adhesion layer by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0107] The metal electrodes 105 are located on both sides of the ITO film 103 and serve as direct contact layers for applied voltage. The deposition of the metal electrodes 105 can effectively reduce the contact resistance of the ITO film-based thermo-optical phase shifter.

[0108] like Figure 19 FIG. 1 is a cross-sectional view of depositing a protective layer 106 on the surface of the indium tin oxide film 103 and the metal electrode. The specific steps include: first, forming an area to be deposited on the indium tin oxide film 103 by patterned photolithography, and then depositing a 20 nm thick Al2O3 layer as the protective layer 106 on the microheater by chemical vapor deposition, physical vapor deposition, electron beam evaporation, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering, or radio frequency magnetron sputtering;

[0109] The protective layer 106 is located above the ITO film 103 and is mainly used to isolate the ITO film 103 from the air and prevent the ITO film 103 from being oxidized when generating Joule heat, thereby reducing device performance.

[0110] like Figure 20As shown in FIG, the structure of the microring resonator (MRR) of the thermo-optical phase shifter including the indium tin oxide thin film is prepared after the above manufacturing steps. The structure of the device is as follows Figure 20 As shown, it is composed of a micro-ring input waveguide 115, a micro-ring output waveguide 116, a ring waveguide 117, an indium tin oxide film 103 and a metal electrode 105;

[0111] The specific device implementation method is to Figure 20 When voltage is applied to the metal electrodes 105 on both sides, the indium tin oxide film 103 generates local Joule heating. The heat is efficiently transferred vertically to the ring waveguide 117 below through the ultra-thin aluminum oxide isolation layer. The refractive index of the waveguide changes due to the increase in temperature, thereby generating a cumulative phase difference in the ring waveguide 117, ultimately achieving modulation of the resonant wavelength, and the optical signal is output by the microring output waveguide 116.

[0112] like Figure 21 As shown in FIG. 1 , the spectrum curve of the microring resonator prepared in Example 2 of the present invention varies with the applied voltage. Figure 20 Applying voltage across the metal electrode 105 generates Joule heating, which changes the waveguide temperature. This thermo-optical effect modifies the waveguide's refractive index, thereby changing the resonant wavelength of the ring waveguide 117. By increasing the voltage amplitude, the resonant wavelength of the microring resonator can be shifted toward longer wavelengths.

[0113] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thermo-optical phase shifter based on indium tin oxide thin film, characterized in that: The thermo-optical phase shifter comprises a protective layer (106), a metal electrode (105), an adhesion layer (104), an indium tin oxide film (103), an isolation layer (102), a silicon waveguide layer (101), and a substrate (100) stacked in sequence; specifically: The substrate (100) is an SOI substrate, the surface of which is patterned, and the substrate (100) comprises a substrate layer and a top silicon layer from bottom to top; The top silicon layer is patterned and photolithographically etched to produce grooves, thereby forming a silicon waveguide layer (101); The isolation layer (102) completely covers the silicon waveguide layer (101); The indium tin oxide film (103) completely covers the isolation layer (102); There are two metal electrodes (105), both of which are long strip structures and are connected to both sides of the indium tin oxide film (103) through an adhesive layer (104); The protective layer (106) is located between the two metal electrodes (105) and completely covers the surface of the indium tin oxide film (103).

2. The thermo-optical phase shifter based on indium tin oxide thin film according to claim 1, characterized in that: A top silicon layer is formed on a substrate (100) by a bonding and peeling method, and the top silicon layer is patterned, photoetched, and etched to form a groove and a silicon waveguide layer (101), wherein the groove is located on both sides of the silicon waveguide layer (101); the groove structure has a width of 1 μm-5 μm, a groove depth of 40 nm-220 nm, and a silicon waveguide layer (101) has a width of 500 nm-3 μm.

3. The thermo-optical phase shifter based on indium tin oxide thin film according to claim 1, characterized in that: The material of the isolation layer (102) is Al2O3, Si3N4 or SiO2, and the thickness is 10nm-200nm; the thickness of the indium tin oxide film (103) is 10nm-300nm.

4. The thermo-optical phase shifter based on indium tin oxide thin film according to claim 1, characterized in that: The material of the adhesion layer (104) is Ti or TiN, the thickness is 10 nm, and the distance between the two adhesion layers (104) is in the range of 5-20 μm.

5. The thermo-optical phase shifter based on indium tin oxide thin film according to claim 1, characterized in that: The metal electrode (105) can be made of Au, Cu, Pt or Ag, with a thickness of 20nm-200nm, and a distance between two metal electrodes (105) is in the range of 5-20μm.

6. The thermo-optical phase shifter based on indium tin oxide thin film according to claim 1, characterized in that: The protective layer (106) can be made of Al2O3, Si3N4 or SiO2, and its thickness is between 20nm and 200nm.

7. A method for preparing a thermo-optical phase shifter based on an indium tin oxide thin film according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1, forming a top silicon layer on the surface of the substrate (100) by bonding and peeling, and performing patterning photolithography and etching on the top silicon layer to form a groove and a silicon waveguide layer (101), wherein the groove is located on both sides of the silicon waveguide layer (101); Step 2, depositing an isolation layer (102) on the silicon waveguide layer (101); Step 3, depositing an indium tin oxide thin film (103) on the isolation layer (102); Step 4: depositing an adhesion layer (104) on the indium tin oxide film (103); the adhesion layer (104) is deposited on the edge positions on both sides of the surface of the indium tin oxide film 102 and forms a connection therewith; Step 5: depositing a metal electrode (105) on the adhesion layer (104); the metal electrode (105) covers the surface of the adhesion layer (104), and the upper surface of the adhesion layer (104) is flush with the lower surface of the metal electrode (105); Step 6: depositing a protective layer (106) on the indium tin oxide film (103); the protective layer (106) completely covers the central area of the surface of the indium tin oxide film (103) by patterned photolithography, and partially covers the metal electrodes (105) located on both sides of the protective layer (106).

8. The method for preparing a thermo-optical phase shifter based on an indium tin oxide thin film according to claim 7, characterized in that: The etching in step 1 is electron beam lithography or plasma etching; the deposition in steps 2 to 6 is chemical vapor deposition, physical vapor deposition, electron beam evaporation coating, pulsed laser deposition, atomic layer deposition, DC magnetron sputtering or radio frequency magnetron sputtering, and the deposition methods in each step may be the same or different.

9. An application of the thermo-optical phase shifter based on an indium tin oxide film according to any one of claims 1 to 6, characterized in that: Preparation of Mach-Zehnder interferometer structure based on thermo-optical phase shifter.

10. The application of the thermo-optical phase shifter based on the indium tin oxide film according to claim 9, characterized in that: The Mach-Zehnder interferometer structure comprises a 1×2 beam splitter (108), an interference arm (109), a holding arm (110), a phase shifter unit (111), a 2×2 beam splitter (112), a first output port (113), and a second output port (114); an MZI modulation unit comprises the interference arm (109), the holding arm (110), and a phase shifter unit (111) integrated in the interference arm (109); specifically: An optical signal is input through an input waveguide (107), an input end of a 1×2 beam splitter (108) is connected to the input waveguide (107), the 1×2 beam splitter (108) splits the optical signal into two paths according to a certain ratio, and the two paths are respectively connected to an interference arm (109) and a holding arm (110), and the interference arm (109) and the holding arm (110) are respectively connected to a first output port (113) and a second output port (114) through a 2×2 beam splitter (112); Voltage is applied to the metal electrodes (105) on both sides of the phase shifter unit (111), and the indium tin oxide film (103) generates local Joule heating. The heat is efficiently and vertically transferred to the silicon waveguide layer (101) below via the ultra-thin isolation layer (102). The refractive index of the waveguide changes due to the temperature increase, thereby accumulating phase differences in the interference arms (109), and ultimately achieving phase modulation of the optical signal.

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