A waveguide modification method based on high temperature induction

Abstract

The application discloses a waveguide modification method based on high-temperature induction, comprising the following steps: adopting a photonic integrated chip, which comprises a substrate and a waveguide; and applying high temperature on the waveguide to obtain a modified waveguide. The application can precisely control the refractive index of the waveguide material by applying high temperature to the local area of the waveguide, thereby permanently compensating for the manufacturing error of an optoelectronic device. Compared with a traditional continuous thermal compensation method, the application does not need to be continuously powered after the compensation is completed, and the energy consumption is significantly reduced. In addition, the application has little influence on the device during the compensation process, and almost no additional loss is introduced, so that the performance of the device is maintained. The application is particularly suitable for precise calibration of large-scale optoelectronic devices, and has important practical value in the field of integrated optics.

Description

Technical Field

[0001] This invention relates to the field of semiconductor photonic integrated circuits, and more specifically to a waveguide modification method based on high temperature induced modification. Background Technology

[0002] Photonic integration achieves optical transceiver and optical routing functions within a compact size by integrating passive devices such as beam splitters and waveguide crossovers, as well as active devices such as modulators and detectors, on the same substrate. Compared to discrete devices, photonic integration can significantly improve chip integration density and shorten on-chip optical interconnect distances, thereby reducing transmission latency and power consumption. Furthermore, with advancements in technologies such as wavelength division multiplexing (WDM) and higher-order modulation formats, photonic integrated chips are making continuous breakthroughs in high-speed data transmission and are widely used in cutting-edge fields such as optical communication, optical computing, and quantum information. However, limited by cost-effectiveness and process precision, photonic integrated devices are inevitably affected by process errors during fabrication. For example, in the fabrication process of silicon-on-insulator (SOI) wafers at an advanced microelectronics foundry in Singapore, ridge etching uses 193nm photolithography with a minimum process linewidth of 140nm. When used to fabricate a 500nm wide ridge waveguide, the typical width error is approximately ±25nm. In the mass production of thin-film lithium niobate chips, a 0.35-micron resolution stepper lithography machine is used, with a typical fabrication error of ±200nm. Furthermore, the top silicon thickness, cladding thickness, and waveguide etching depth of SOI, silicon nitride, and thin-film lithium niobate wafers all exhibit manufacturing errors within a certain range. The accumulation of these various process errors causes phase deviations in the optical modes within the waveguide, thus affecting device performance. Mach-Zehnder interferometers (MZI) and microring resonators (MR) are particularly significantly affected. For MZI structures, process errors cause random phase differences between the phase-shifting arms, making the initial state of the MZI unpredictable. For MR structures, process errors often cause the resonant wavelength to deviate from the design value, thus affecting its filtering or channel selection functions. A common compensation strategy is to continuously thermally tune the refractive index of the waveguide material to calibrate the phase difference between the two arms of the MZI and the resonant wavelength of the MR to ideal values. However, in large-scale integrated systems, thermal tuning not only continuously increases power consumption but also significantly increases the complexity of electrical control and packaging, placing higher demands on system energy efficiency and stability. In response, a series of permanent post-processing solutions such as femtosecond laser processing and germanium doping have been proposed. However, these methods introduce additional losses, are complex to process, and are costly, thus facing many challenges in large-scale commercial applications.

[0003] In conclusion, it is essential to propose a non-destructive, non-volatile, and efficient post-processing solution to compensate for process errors. Summary of the Invention

[0004] This invention proposes a high-temperature-induced waveguide modification method, which is a non-destructive, efficient, and non-volatile method for compensating for process errors based on localized high-temperature heat treatment. This method achieves precise control of the refractive index of the waveguide material by applying short-term high-temperature treatment to a localized region of the waveguide, thereby permanently compensating for manufacturing errors in optoelectronic devices. Compared to traditional continuous thermal tuning compensation methods, this invention requires no continuous power supply after compensation, significantly reducing energy consumption. Furthermore, this invention has minimal impact on the device during the compensation process, introducing almost no additional losses, thus maintaining device performance. This invention is particularly suitable for the precise calibration of large-scale optoelectronic devices and has significant practical value in the field of integrated optics.

[0005] A waveguide modification method based on high temperature induction includes the following steps:

[0006] It employs a photonic integrated chip, including: a substrate and a waveguide;

[0007] A modified waveguide is obtained by applying high temperature to the waveguide.

[0008] The high temperature is greater than or equal to the yield temperature of the waveguide, but less than the melting point of the waveguide material. The high temperature causes local lattice deformations such as dislocation bending and lattice expansion in the waveguide material, or even amorphization, which reduces the real part of the refractive index of the waveguide material without significantly affecting its optical absorption characteristics.

[0009] A laser external to the photonic integrated chip, a thermal resistor inside the photonic integrated chip, or a doped structure inside the photonic integrated chip is used as a heat source to apply high temperature to the waveguide.

[0010] The aforementioned photonic integrated chip also includes:

[0011] A cladding layer is disposed on the substrate, and the waveguide is disposed within the cladding layer. Hollow cladding spaces are formed on both sides of the waveguide. The waveguide and the cladding layer surrounding it constitute a waveguide assembly. The hollow cladding spaces serve as thermal insulation spaces. A substrate hollow space is also provided on the substrate corresponding to the hollow cladding spaces and the waveguide assembly. This substrate hollow space provides thermal insulation for both the substrate and the waveguide assembly. The hollow space ensures that the waveguide assembly is surrounded by air with low thermal conductivity, preventing heat generated by the heat source from dissipating to the chip substrate. Instead, the heat is concentrated within the waveguide, generating the high temperature.

[0012] The aforementioned photonic integrated chip is a chip for a Mach-Zehnder interferometer.

[0013] The chip of the Mach-Zehnder interferometer includes:

[0014] Substrate;

[0015] A cladding layer disposed on the substrate;

[0016] An input waveguide, an input beam splitter / combiner, a phase-shifting arm waveguide, a resistive heat source, an output beam splitter / combiner, and an output waveguide are disposed within the cladding.

[0017] The input waveguide, input beam splitter / combiner, phase-shifting arm waveguide, output beam splitter / combiner, and output waveguide are connected in sequence, and the resistive heat source is disposed around the phase-shifting arm waveguide.

[0018] Applying high temperature to the waveguide specifically includes: a resistive heat source in the Mach-Zehnder interferometer chip applying high temperature through heating. The heat generated by the resistive heat source raises the temperature of the phase-shifting arm waveguide to the aforementioned high temperature. The resulting thermal stress causes plastic deformation or even amorphization of the waveguide material lattice, thereby modifying the real refractive index of the phase-shifting arm waveguide material. Ultimately, this achieves a redistribution of light intensity at the output end of the Mach-Zehnder interferometer structure, for example, allowing all light intensity to be output to any port, thus achieving the purpose of compensating for process errors.

[0019] The aforementioned photonic integrated chip is a microring resonator chip, and the microring resonator chip includes:

[0020] Substrate;

[0021] A cladding layer disposed on the substrate;

[0022] And a ring-shaped phase-shifting waveguide, a transmission waveguide, and a resistive heat source disposed within the cladding;

[0023] The transmission waveguide is coupled to the ring phase-shift waveguide, and the resistive heat source is disposed around the ring phase-shift waveguide.

[0024] Applying high temperature to the waveguide specifically includes: a resistive heat source in the microring resonator chip applying high temperature through heating. The heat generated by the resistive heat source raises the temperature of the ring phase-shift waveguide to the high temperature. The resulting thermal stress causes plastic deformation or even amorphization of the ring waveguide material lattice, thereby modifying the real refractive index of the ring waveguide material. Ultimately, this causes a shift in the resonant wavelength of the microring resonator chip, achieving the purpose of compensating for process errors.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1) Compared to traditional continuous thermal adjustment compensation schemes, the waveguide state in this invention is irreversible once adjusted.

[0027] It requires no continuous power supply, thus significantly reducing energy consumption and alleviating the packaging and electric drive burden of optoelectronic devices;

[0028] 2) Compared with post-processing methods such as femtosecond laser processing and germanium doping, this invention does not introduce additional losses, ensuring stable device performance;

[0029] 3) Compared with waveguide surface manipulation by femtosecond lasers and other methods, this invention achieves efficient optical property manipulation by uniformly heating the entire waveguide at local high temperatures. In addition, this invention provides the possibility for precise compensation, repeatability and high reliability of post-processing by precisely controlling local high temperatures.

[0030] 4) This invention has a wide range of applications and is suitable for various photonic integration platforms such as SOI, silicon nitride, and thin-film lithium niobate. It is also suitable for various optoelectronic integrated devices such as MZI initial phase calibration and micro-ring resonator resonant wavelength calibration. It is particularly suitable for the precise calibration of large-scale optoelectronic devices and has important practical value in the field of integrated optics.

[0031] 5) In particular, a suspended waveguide-type thermally modulated structure is used in the specific implementation to achieve local high temperature, further complete waveguide modification and permanent process error compensation. This scheme is compatible with the fabrication process of photonic integrated devices, requires no special process or additional equipment, and reduces post-processing costs. The post-processing process can be started simply by supplying power to the heat source in the suspended waveguide-type thermally modulated structure. The operation is simple.

[0032] In summary, this invention provides, for the first time, a highly efficient, non-volatile, and nearly non-destructive post-compensation scheme to address the unavoidable fabrication errors of optoelectronic devices at limited process nodes. This scheme is applicable to various photonic integration platforms, optoelectronic devices, and various potential heating methods. Attached Figure Description

[0033] Figure 1 A specific structure for achieving localized high temperature—a suspended waveguide-type thermally modulated structure: (a) 3D view, (b) 2D cross-sectional view;

[0034] Figure 2 (a) Temperature change of the phase-shifting arm waveguide along the transmission direction after a high-voltage excitation is applied to a heat source in a suspended waveguide-type local high-temperature structure; (b) Test of the heating and cooling rate of the waveguide by the heat source.

[0035] Figure 3 A schematic diagram of an MZI chip with a suspended waveguide-type local high-temperature structure;

[0036] Figure 4 The following are the measured optical power curves of the through and cross output ports in MZI unit 1 after each excitation: (a) and (b) the measured total optical power curve of the output ports in MZI unit 1.

[0037] Figure 5 The measured power consumption-optical power (PT) curves of the two output ports in MZI unit 1 are: (a) before compensation, (b) after the 3rd excitation, and (c) after the 16th excitation.

[0038] Figure 6The curve showing the change in the percentage of through ports of MZI unit 1 after the last excitation as a function of rest time;

[0039] Figure 7 The PT curves of the two output ports in MZI unit 2 were measured: (a) before excitation, (b) after excitation;

[0040] Figure 8 A schematic diagram of a microring resonator chip with a suspended waveguide-type local high-temperature structure;

[0041] Figure 9 The spectral curves of the microring resonator before and after applying local high temperature. Detailed Implementation

[0042] The technical solution of the present invention will be described in detail below, and one example of a local high temperature realization method based on a suspended waveguide thermally modulated structure will be used to apply it to the process error compensation of MZI structure and micro-ring structure to verify the technical advantages and beneficial effects of the present invention.

[0043] In the manufacturing process of photonic integrated circuits, due to process errors, the structural parameters of the device may deviate from the design values, leading to a decline in device performance. This invention proposes a method for permanent modification of optical waveguides and compensation for process errors based on local high-temperature induced modification. The specific compensation process is as follows: First, the local waveguide is rapidly and uniformly heated using heating methods. When the waveguide temperature exceeds its yield temperature, atoms in the waveguide material diffuse at an accelerated rate, and thermal stress accumulates significantly, exceeding the yield strength. This leads to irreversible plastic deformations such as lattice micro-bending and lattice expansion, and even local amorphization. Under the synergistic effect of plastic deformation, phase transition, high temperature, and stress, the real part of the refractive index of the waveguide material undergoes permanent adjustment. Therefore, it is possible to permanently compensate for process errors of photonic devices at specific process nodes, including but not limited to calibrating the phase difference between MZI phase shift arms to improve device consistency and stability; adjusting the resonant wavelength of microring resonators to compensate for manufacturing errors or environmental influences, and improving filtering accuracy and modulation performance. The compensation effect of this invention is non-volatile; once adjustment is complete, the device remains stable for a long period without continuous power supply. Compared to traditional continuous thermal tuning schemes, it significantly reduces power consumption and diminishes the electrical drive and packaging requirements associated with compensation. This invention enables uniform heating of local waveguides with a wide adjustment range; it avoids material damage, exhibiting near-lossless adjustment characteristics; and it achieves high-precision adjustment through temperature control, ensuring the accuracy of error compensation. This solution is applicable to various photonic integration platforms such as SOI, thin-film lithium niobate, and silicon nitride, and can be used for phase calibration of optoelectronic devices such as MZI or microring resonator-type optical switches, modulators, and filters. Therefore, it has a wide range of applications and good scalability.

[0044] It is worth noting that methods for achieving localized high temperatures in waveguides include, but are not limited to, driving conventional on-chip heat sources with ultra-high voltage and adding heat dissipation limiting structures to improve heating efficiency. Here, a suspended waveguide thermally modulated structure is used as a specific implementation method to achieve short-term localized high temperatures. This method is compatible with mainstream optoelectronic integrated manufacturing platforms and is cost-effective. Although suspended waveguide thermally modulated structures have been widely used in optoelectronic devices, this invention is the first to utilize the localized high-temperature characteristics of this structure and apply it for permanent post-compensation of process errors. Figure 1 (a) is a three-dimensional diagram of the suspended waveguide-type local high-temperature structure used in this invention. The X, Y, and Z directions are the optical transmission direction, the waveguide width direction, and the chip height direction, respectively. Figure 1 (b) is along Figure 1 (a) shows the YZ cross-section diagram drawn with dashed lines. 1-1 is the substrate, 1-2 is the waveguide for light transmission, 1-3, 1-3-1, 1-3-2, and 1-3-3 are the cladding layers, and 1-4 is the heat source. Powering its two ends achieves a heating effect, which is simple to operate and provides the possibility for precise control of the waveguide material's refractive index. To simplify the model, the power supply electrodes at both ends of the thermal resistor along the waveguide transmission direction are ignored here, but these electrodes are indispensable in practical applications. 1-5 is the hollow cladding layer on both sides of the waveguide. Waveguide 1-2 and the cladding layer 1-3-2 surrounding the waveguide constitute waveguide assembly 1-6. The hollow cladding layer 1-5 and the substrate below waveguide assembly 1-6 have a hollow substrate 1-7. The hollow cladding layer 1-5 and the hollow substrate 1-7 make waveguide assembly 1-6 a suspended waveguide assembly. The suspended waveguide assembly 1-6 and the heat source 1-4 constitute a suspended waveguide thermal tuning structure. It is worth noting that since no suspended structure is formed at both ends of the waveguide along the X direction (see...),... Figure 1 (a)) thus providing sufficient support for the suspended waveguide assembly in the middle section. Figure 1 (b) The cross-section of the suspended waveguide is clearly shown. A common method for achieving a hollow substrate is to first fully etch the cladding on both sides of the waveguide to form a hollow cladding, then inject a special gas or etchant into the hollow cladding to etch or corrode away the hollow cladding and the substrate beneath the waveguide assembly, ultimately resulting in the transmission waveguide being surrounded by air. It is worth noting that waveguides 1-2 and cladding 1-3 are only illustrative and can also be complex waveguide structures and complex claddings. The heat source 1-4 in this invention is not limited to the resistance temperature detector (RTD) heat source above the waveguide; other heat sources, such as doped heat sources, are also applicable. An external electrical signal is applied to both ends of the heat source via electrodes. Based on the Joule effect, electrical energy is converted into heat energy and transmitted to the waveguide. Because the suspended waveguide is surrounded by air (1-5) with low thermal conductivity, very little heat will leak to the substrate 1-1, and most of the heat will remain in the waveguide assembly 1-6. Therefore, by adjusting the electrical signal, localized high temperatures near the heat source can be achieved, and the waveguide temperature can be precisely controlled.

[0045] Taking the SOI platform as an example, in the suspended waveguide-type thermally modulated structure, the length of the waveguide and its thermal resistor is set to 90 μm, and the thermal resistor is made of titanium nitride with a resistance of 400 Ω. When a high driving voltage is applied across the thermal resistor, a large amount of Joules generated is conducted to the phase-shifting arm waveguide and changes the temperature of the waveguide material. Figure 2 (a) The temperature of the phase-shifting arm waveguide material along the optical transmission direction was simulated as a function of the excitation high voltage. When the excitation high voltage is 2.5V, the center temperature of the phase-shifting arm waveguide is about 1100K, which is the yield temperature of silicon (usually 900K-1100K); as the power consumption increases, the local temperature of the waveguide also increases further. Figure 2 (b) Tests showed that the waveguide's heating and cooling times under these parameters were all in the millisecond range. It is noteworthy that even with heating and cooling times in the second range, waveguide modification effects still occur as long as the high-temperature conditions described in this invention are met. This suspended waveguide-type locally high-temperature thermally modulated structure is used in subsequent MZI and microring resonator embodiments to achieve waveguide modification and refractive index modulation of the waveguide material under local high-temperature induction.

[0046] Example 1: Post-processing compensation of MZI chip 1 is performed using a suspended waveguide-type local high-temperature structure to achieve waveguide modification and precise cross-state.

[0047] Will Figure 1 The suspended waveguide-type local high-temperature structure was applied to a 2×2 MZI chip on the SOI platform for verification. Figure 3 The diagram shows a three-dimensional representation, where: 2-1 is a silicon substrate, 2-2 is a silicon waveguide, 2-3 is a silicon oxide cladding, 2-4 is a resistance-type heat source, 2-5 and 2-6 are the input and output waveguides, respectively; 2-7 and 2-8 are the input and output beam splitters and combiners, respectively; 2-9 is the phase-shifting arm waveguide to be compensated; 2-9 and its surrounding cladding constitute a waveguide assembly; 2-10 is a hollow cladding structure. After etching and other treatments, the hollow cladding 2-10 and the substrate beneath the waveguide assembly are removed. Therefore, the resistance thermometer 2-4, the waveguide 2-9, and the cladding surrounding the waveguide together constitute a suspended waveguide-type locally high-temperature thermally tuned structure, whose parameters are similar to... Figure 2The simulation parameters in (a) are consistent. To simplify the schematic diagram, metal electrodes are not drawn across resistors 2-4 along the light transmission direction. In practical applications, voltage is applied to the electrodes across 2-4 to excite them as heat sources for heat dissipation. In the embodiment, the suspended waveguide-type thermally modulated structure generates local high temperatures under high-voltage excitation, inducing irreversible optical modification of the real part of the refractive index of the waveguide material to be processed, thereby adjusting the phase difference of the beam between the two phase shift arms of the MZI, and further realizing the redistribution of the output light intensity of the MZI, such as realizing cross-output of all light intensity (input and output ports on different sides) or through output (input and output ports on the same side), etc., and then used in specific applications of MZI-type optical switches and modulators. In addition, the suspended waveguide-type thermally modulated structure does not achieve permanent refractive index modulation under low-voltage excitation, so it can be used as a reversible conventional thermally modulated phase shifter under low voltage, combined with MZI to form a thermo-optical switch, further demonstrating the change of the thermo-optical switch state before and after processing. In the specific test, a low voltage was first applied to the suspended waveguide-type locally high-temperature structure, and the initial power consumption-optical power (PT) curve of the MZI switch was obtained by scanning. Subsequently, a 2.5V high-voltage excitation with millisecond-level rapid temperature rise and fall was applied, generating a high temperature of 1100K locally in the waveguide (see...). Figure 2 (a) The excitation time is 15 seconds, which produces an irreversible compensation effect on the real refractive index of the waveguide material. After the high voltage is removed, the PT curve is scanned again under low voltage drive. Due to the change in the initial phase shift, the corresponding curve is shifted. Since the local refractive index adjustment is difficult to monitor directly, we indirectly reflect the refractive index change of the phase-shifting arm waveguide by changing the intensity at the MZI output terminal. The high voltage excitation of 2.5V for 15 seconds is repeated, and the PT curves under low voltage after each excitation are recorded. The initial state of the PT curves before and after excitation clearly reflects the modification of the phase-shifting arm waveguide material, proving the beneficial effect of this invention.

[0048] In actual measurements, light is input from the upper input waveguide, the upper output waveguide is defined as a through port, and the lower output waveguide is defined as a cross port. Figure 4(a) shows the measured optical power variation curves of the through and cross ends in MZI unit 1 after each excitation, all measured after the voltage excitation was canceled after processing. When the sequence number is 0, it corresponds to the initial response before compensation. At this time, the cross end output is dominant, and the cross-talk at the through end is about -14dB. According to test experience, the typical cross-talk should be lower than -20dB, so the ideal cross-talk state is not achieved. After 16 processing steps, the optical power distribution of the two output ports changed significantly: after the first three processing steps, the crosstalk at the through end was significantly reduced, especially after the third processing step (cumulative excitation time of 45 seconds), when the crosstalk at the through end dropped to -24dB, achieving a precise crossover state. For applications that want the initial state to be crossover, the process error compensation was completed at this point. Starting from the fourth high-voltage excitation, the optical power at the through end increased, while the optical power at the crossover end decreased accordingly. By the 16th processing step (cumulative excitation time of 4 minutes), the difference in optical power between the two output ports had decreased to 1.15dB, indicating that the present invention has a wide adjustment range, and further compensation can achieve a through state. Figure 4 (b) The total optical power of the two output ports after each excitation is shown. Overall, it remains around -2.85dBm. The loss fluctuates slightly after individual excitations, mainly due to test errors.

[0049] After each excitation, we also recorded the PT transfer curves of the two output ports of MZI unit 1 under low voltage scanning. Figure 5 (a), (b), and (c) correspond to the curves after no compensation, the 3rd excitation, and the 16th excitation, respectively. Due to the post-processing altering the initial state (0mW), the PT curve shifts overall. As mentioned earlier, after the third post-processing, MZI cell 1 is in a perfect crossover state at 0mW, and its PT curve is shown below. Figure 5 (b) Calculations showed that the changes in the real part of the waveguide material's refractive index after the 3rd and 16th high-voltage excitations (i.e., high-temperature induction) were -0.0009 and -0.0049, respectively, while the imaginary part remained almost unchanged. After 16 processing cycles, the chip was left to stand. Over the following four and a half months, the output optical power of MZI unit 1 was tested multiple times without pressure, and the percentage of optical power at the through-hole was calculated. Figure 6 As shown in the figure. The results show that this percentage remained almost unchanged over 135 days, hovering around 44%, demonstrating the non-volatile nature of the described treatment method.

[0050] Example 2: Post-processing compensation of MZI chip 2 is performed using a suspended waveguide-type local high-temperature structure to achieve waveguide modification and precise through-state.

[0051] The device parameters used in this embodiment are the same as those in Embodiment 1, and an excitation experiment was conducted on it. Figure 7(a) shows the measured PT curve of the untreated MZI unit 2, where the output at the through end is dominant in the initial state (0mW), but the crosstalk at the cross end is as high as -6.4dB, indicating that the through state is not perfect. A floating waveguide-type local high-temperature structure was used to repeatedly apply millisecond-level rapid heating and cooling high-voltage excitation to the MZI unit 2, where the high voltage duration was 5s and the excitation voltage was 3V, corresponding to a local high temperature of 1400K (see...). Figure 2 (a)) until it achieves a precise through state. After accumulating excitation for 40 seconds, the corresponding measured PT curve is as follows. Figure 7 As shown in (b), the crosstalk at the crossover end is reduced to approximately -34 dB, which is at the trough of the PT curve, while the loss of MZI element 2 remains almost unchanged. This demonstrates the effect of waveguide modification, achieving a perfect straight-through state through post-compensation.

[0052] Example 3: Post-processing compensation of micro-ring resonator chips is achieved using a suspended waveguide-type local high-temperature structure to realize waveguide modification and resonant wavelength calibration.

[0053] This suspended waveguide-type local high-temperature structure was applied to the microring resonator structure of the SOI platform for verification. Figure 8 A three-dimensional schematic diagram is provided, where: 3-1 is a silicon substrate, 3-2 is a silicon oxide cladding, 3-3 and 3-4 are silicon waveguides, 3-3 is a transmission waveguide, 3-4 is a ring-shaped phase-shifting waveguide, and 3-5 is a resistive heat source. Hollow cladding layers 3-6 are located on both sides of the ring-shaped waveguide 3-4. The substrate beneath the hollow cladding layers 3-6 and part of the ring-shaped phase-shifting waveguide 3-4 is removed, resulting in a suspended waveguide-type locally high-temperature thermally modulated structure formed by the ring-shaped waveguide 3-4 and the thermal resistor 3-5. For simplification, the driving electrodes connected to the two ends of the thermal resistor 3-5 are not included. In practical applications, a voltage is applied to the two electrodes connected to the thermal electrodes to excite them as a heat source for heat dissipation. The suspended waveguide-type thermally modulated structure generates local high temperatures under high-voltage excitation, inducing irreversible real part modification of the optical refractive index of the waveguide material to be processed, thereby adjusting the phase difference of the beam around the ring, causing a shift in the wavelength that satisfies the resonance condition, ultimately achieving the shift and calibration of the micro-ring resonant wavelength.

[0054] In this embodiment, the radius of the microring resonator is 30 μm, and the total length of the suspended waveguide-type local high-temperature structure is 100 μm. Its initial resonance spectrum is as follows: Figure 9 As shown by the black curve in the figure, the free spectral range, i.e., the resonant period, is 2.5 nm, with one resonant wavelength λ0 at 1294.44 nm. By applying a high-voltage excitation of 2.5 V to the thermistor, which causes millisecond-level rapid heating, a local temperature of approximately 1100 K is generated in the waveguide (see...). Figure 2(a) This will reduce the real part of the refractive index of the ring waveguide without additional loss. Referring to the typical refractive index changes of -0.0009 and -0.0049 obtained from tests in Example 1, when the micro-ring waveguide material is introduced to the same temperature using the local high-temperature post-processing method, the same amount of refractive index change is obtained. Simulations show the spectrum of the micro-ring resonator after local high-temperature treatment as follows: Figure 9 As shown by the dark gray and light gray curves, λ0 has shifted to the left to 1294.272 nm and 1293.529 nm, respectively, representing blue shifts of 0.07 and 0.37 resonant periods. Therefore, the resonant wavelength shift of the microring resonator was achieved through local high-temperature processing with almost no impact on the spectral line shape. Ultimately, this local high-temperature post-processing method can be used to calibrate the initial random resonant wavelength of the microring resonator to the designed resonant wavelength.

Claims

1. A waveguide modification method based on high temperature induction, characterized in that, Includes the following steps: It employs a photonic integrated chip, including: a substrate and a waveguide; A modified waveguide is obtained by applying high temperature to the waveguide. The high temperature mentioned refers to a temperature greater than or equal to the yield temperature of the waveguide material and less than the melting point of the waveguide material. A high temperature of 1100 K is applied to the waveguide by using an external laser, a thermal resistor inside the photonic integrated chip, or a doped structure inside the photonic integrated chip as a heat source. The aforementioned photonic integrated chip also includes: A cladding layer is disposed on the substrate, and a waveguide is disposed within the cladding layer. Hollow cladding layers are provided on both sides of the waveguide. The waveguide and the cladding layer surrounding the waveguide constitute a waveguide assembly. The hollow cladding layer serves as a heat insulation space. A substrate hollow is provided on the substrate corresponding to the cladding hollow and the waveguide component, and the substrate hollow serves as a thermal insulation space for the substrate and the waveguide component.

2. The waveguide modification method based on high temperature induction according to claim 1, characterized in that, The aforementioned photonic integrated chip is a chip for a Mach-Zehnder interferometer.

3. The waveguide modification method based on high temperature induction according to claim 2, characterized in that, The chip of the Mach-Zehnder interferometer includes: Substrate; A cladding layer disposed on the substrate; An input waveguide, an input beam splitter / combiner, a phase-shifting arm waveguide, a resistive heat source, an output beam splitter / combiner, and an output waveguide are disposed within the cladding. The input waveguide, input beam splitter / combiner, phase-shifting arm waveguide, output beam splitter / combiner, and output waveguide are connected in sequence, and the resistive heat source is disposed around the phase-shifting arm waveguide.

4. The waveguide modification method based on high temperature induction according to claim 3, characterized in that, Applying high temperatures to the waveguide specifically includes: The resistive heat source in the Mach-Zehnder interferometer chip applies high temperature by generating heat.

5. The waveguide modification method based on high temperature induction according to claim 1, characterized in that, The aforementioned photonic integrated chip is a microring resonator chip, and the microring resonator chip includes: Substrate; A cladding layer disposed on the substrate; And a ring-shaped phase-shifting waveguide, a transmission waveguide, and a resistive heat source disposed within the cladding; The transmission waveguide is coupled to the ring phase-shift waveguide, and the resistive heat source is disposed around the ring phase-shift waveguide.

6. The waveguide modification method based on high temperature induction according to claim 5, characterized in that, Applying high temperatures to the waveguide specifically includes: The resistive heat source in the microring resonator chip applies high temperature by generating heat.

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