Method and device for measuring direct-current offset degree of thin-film lithium niobate electro-optical modulator

Abstract

The invention discloses a method and device for measuring the direct-current offset degree of a thin-film lithium niobate electro-optical modulator, and the method comprises the steps: providing a micro-ring resonator of a double-ring cascade structure, and enabling the micro-ring resonator to be prepared based on a thin-film lithium niobate substrate; applying an external electric field to a modulation area of the micro-ring resonator, and acquiring an optical signal output by the resonator in real time through a data acquisition system; according to the collected optical signal, extracting wavelength variation delta lambda of a micro-ring harmonic peak under different duration time; quantitatively representing the direct-current drift degree of the thin-film lithium niobate electro-optical modulator based on the wavelength variation delta lambda; the method is suitable for direct current drift measurement with high precision and long-time stability, is especially suitable for scenes requiring direct current drift phenomenon research, and can provide more reliable experimental data support for related research.

Description

Technical Field

[0001] The present invention relates to a measuring method and a device, and in particular to a measuring method and a device for the DC offset degree of a thin-film lithium niobate electro-optical modulation device. Background Art

[0002] In fields such as optical communications and sensing, thin-film lithium niobate electro-optical modulators are widely used in various optical integrated devices due to their excellent performance. Due to its excellent electro-optic coefficient, fast response time, and high integration density, thin-film lithium niobate has become an important material for building high-performance optical modulators. However, in practical applications, the performance of thin-film lithium niobate electro-optical modulators is often affected by factors such as the fabrication process and substrate quality, resulting in a drift in the static operating point, known as DC drift. This drift not only affects the device's performance stability but can, in severe cases, lead to device failure, posing a challenge to the long-term reliable operation of optical communication systems and sensing equipment.

[0003] Currently, the common method for evaluating DC drift is to characterize it through changes in optical power, but this method has several limitations. First, the measurement process is easily affected by various factors, such as light source stability, detector sensitivity, and overall system stability, resulting in unstable measurement results. Second, traditional measurement methods require the test system to have extremely high long-term stability, which is difficult to achieve in practical applications. Furthermore, for DC drift measurements requiring high precision and long-term stability, existing technical means often cannot meet the requirements, limiting further optimization and application of device performance.

[0004] Therefore, there is an urgent need to develop a more stable and accurate method to measure the DC offset of thin-film lithium niobate electro-optical modulators. An ideal measurement method should overcome the shortcomings of existing technologies, improve the long-term stability and accuracy of test results, and provide more reliable experimental data support for DC drift research, thereby promoting the further development and application of integrated optical devices. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for measuring the DC offset degree of a thin-film lithium niobate electro-optical modulator device to analyze and compare the DC drift effect under different electric fields, improve the stability and accuracy of the measurement results, and on the other hand, provide a device for implementing the measurement method.

[0006] Technical solution: The measurement method of the present invention comprises:

[0007] S1. Providing a microring resonator with a dual-ring cascade structure, wherein the microring resonator is prepared based on thin-film lithium niobate;

[0008] S2, applying an external electric field to the modulation region of the microring resonator, and collecting the optical signal output by the resonator in real time through a data acquisition system;

[0009] S3. Extract wavelength variations Δλ of the microring resonance peaks at different durations based on the collected optical signals, and quantitatively characterize the DC drift degree of the thin-film lithium niobate electro-optical modulation device based on the wavelength variations Δλ.

[0010] Preferably, the microring resonator of the dual-ring cascade structure in step S1 includes a ladder-type waveguide, and the ladder-type waveguide is formed on the lithium niobate thin film by an etching process.

[0011] Preferably, electrodes are provided on the inner side and the outer side of the trapezoidal waveguide, respectively, and the electrodes are used to apply an external electric field to the waveguide.

[0012] Preferably, when an external electric field is applied in step S2, the refractive index of the thin film lithium niobate waveguide changes due to the electro-optic effect, and the microring resonance peak wavelength is initially shifted.

[0013] Preferably, in step S3, the continuous change Δλ of the resonance peak wavelength is monitored to reflect the secondary change of the refractive index caused by the weakening of the external electric field due to the DC drift effect.

[0014] Preferably, step S3 further comprises distinguishing the resonance peaks of the two micro-rings in the dual-ring cascade structure, and independently quantifying the DC drifts of different modulation regions by analyzing the morphological changes of each resonance peak.

[0015] The device for implementing the measurement method according to the present invention comprises:

[0016] Substrate, a buried oxide layer located above the substrate;

[0017] A ladder-shaped waveguide formed on the substrate, the ladder-shaped waveguide being located on the buried oxide and formed by etching for light transmission;

[0018] A first electrode and a second electrode are provided on both sides of the inner and outer sides of the ladder-shaped waveguide;

[0019] Data acquisition system, used to monitor the change of resonance peak wavelength in real time;

[0020] A double-ring cascaded microring resonator is coupled to the ladder waveguide.

[0021] Preferably, the material of the substrate is silicon, and the material of the buried oxide layer is silicon dioxide.

[0022] Preferably, the material of the ladder-type waveguide is thin-film lithium niobate, and the thickness of the thin-film lithium niobate is 0.6 um.

[0023] The device according to claim 7, further comprising a grating.

[0024] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: 1. Through the dual-ring cascade structure, the optical power change caused by DC drift is converted into the wavelength change of the microring resonance peak, thereby realizing the quantitative measurement of DC drift. This method mainly relies on the change of the microring resonance peak wavelength, avoiding the problem that the optical power is easily affected by multiple factors in the traditional method, and significantly improving the long-term stability and accuracy of the test results; 2. By monitoring the change in the resonance peak wavelength to quantitatively characterize the size and change trend of DC drift, no complex optical power processing system is required, which greatly simplifies the test difficulty and reduces the test cost; 3. By using the change in the microring resonance peak wavelength to characterize DC drift, compared with the traditional method that directly relies on the change in optical power, it can more accurately reflect the influence of the external electric field on the refractive index of the thin film lithium niobate waveguide, and is not easily disturbed by the optical power fluctuation inside the microring; 4. By distinguishing the coupling state of the two microring resonators, the DC drift effect under different electric fields can be effectively distinguished, thereby improving the accuracy and reliability of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a top view of the test structure of the present invention;

[0026] Figure 2 Schematic diagram of the cross section of the waveguide of the present invention;

[0027] Figure 3 Schematic diagram of the test results of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0029] A method for measuring the DC offset of a thin-film lithium niobate electro-optical modulator device comprises the following steps:

[0030] S1. Take a thin film of lithium niobate with a thickness of 0.6 μm and bond it to a silicon substrate through a silicon dioxide buried oxide layer; use electron beam lithography and reactive ion etching technology to etch a ladder-shaped waveguide on the surface of the thin film of lithium niobate, and prepare micro-ring electrodes on the ladder-shaped waveguide. The electrodes are arranged on the inner and outer sides of the ladder-shaped waveguide to form a micro-ring resonator with a double-ring cascade structure.

[0031] S2. Apply an external electric field to the modulation region of the microring resonator, collect the optical signal output by the resonator in real time through the data acquisition system, and record the changes in the resonance peak wavelength at different durations.

[0032] S3. Analyze the resonance peak wavelength change data, process the collected optical signal, extract the wavelength change Δλ of the microring resonance peak at different durations based on the collected optical signal, and quantitatively characterize the DC drift degree of the thin film lithium niobate electro-optical modulation device based on the wavelength change Δλ.

[0033] An apparatus for carrying out the measurement method, comprising:

[0034] Silicon substrate, silicon dioxide buried oxide layer, thin film lithium niobate ladder waveguide, electrodes, data acquisition system, dual-ring cascaded microring resonator and grating.

[0035] A silicon substrate, a silicon dioxide buried oxide layer is located on the silicon substrate, and a thin-film lithium niobate ladder waveguide is formed on the silicon substrate and located on the buried oxide layer. The ladder waveguide is formed by etching the thin-film lithium niobate, and the ladder waveguide is used for light transmission;

[0036] A first electrode and a second electrode are provided on both sides of the ladder-shaped waveguide;

[0037] Data acquisition system, used to monitor the change of resonance peak wavelength in real time;

[0038] Dual-ring cascaded microring resonator coupled with a ladder waveguide.

Claims

1. A method for measuring the DC offset of a thin-film lithium niobate electro-optical modulator, characterized in that: The following steps are involved: S1. Providing a microring resonator with a dual-ring cascade structure, wherein the microring resonator is prepared based on thin-film lithium niobate; S2, applying an external electric field to the modulation region of the microring resonator, and collecting the optical signal output by the resonator in real time through a data acquisition system; S3. Extract wavelength variations Δλ of the microring resonance peaks at different durations based on the collected optical signals, and quantitatively characterize the DC drift degree of the thin-film lithium niobate electro-optical modulation device based on the wavelength variations Δλ.

2. The measuring method according to claim 1, wherein The microring resonator with the dual-ring cascade structure in step S1 includes a ladder-type waveguide, which is formed on a thin-film lithium niobate by an etching process.

3. The measuring method according to claim 2, characterized in that Electrodes are respectively provided on the inner side and the outer side of the trapezoidal waveguide, and the electrodes are used to apply an external electric field to the waveguide.

4. The measuring method according to claim 1, wherein When an external electric field is applied in step S2, the refractive index of the thin film lithium niobate waveguide changes due to the electro-optic effect, and the microring resonance peak wavelength is initially shifted.

5. The measuring method according to claim 1, wherein: In step S3, the continuous change Δλ of the resonance peak wavelength is monitored to reflect the secondary change of the refractive index caused by the weakening of the external electric field due to the DC drift effect.

6. The measuring method according to claim 1, characterized in that Step S3 also includes distinguishing the resonance peaks of the two micro-rings in the dual-ring cascade structure, and independently quantifying the DC drift of different modulation regions by analyzing the morphological changes of each resonance peak.

7. A device for implementing the measurement method according to any one of claims 1 to 6, characterized in that: include: Substrate, a buried oxide layer located above the substrate; A ladder-shaped waveguide formed on the substrate, the ladder-shaped waveguide being located on the buried oxide and formed by etching for light transmission; A first electrode and a second electrode are provided on both sides of the inner and outer sides of the ladder-shaped waveguide; Data acquisition system, used to monitor the change of resonance peak wavelength in real time; A double-ring cascaded microring resonator is coupled to the ladder waveguide.

8. The device according to claim 7, characterized in that The material of the substrate is silicon, and the material of the buried oxide layer is silicon dioxide.

9. The device according to claim 7, characterized in that The material of the ladder-shaped waveguide is thin-film lithium niobate, and the thickness of the thin-film lithium niobate is 0.6 um.

10. The device according to claim 7, characterized in that Also includes gratings.

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