A method for testing half-wave voltage of a silicon optical chip

Abstract

The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind of half-wave voltage test methods of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind to half-wave voltage test method of silicon optical chip, belong to silicon optical chip test technical field.The application discloses a kind kind to half-wave voltage test method of silicon optical chip, belong to silicon optical chip test technical fields.

Description

Technical Field

[0001] This invention relates to the field of silicon photonics chip testing technology, and specifically to a method for testing the half-wave voltage of a silicon photonics chip. Background Technology

[0002] In silicon photonics chips, the Mach-Zehnder modulator (MZM) is a key component for achieving high-speed electro-optic signal conversion. Half-wave voltage is a core parameter for measuring MZM modulation efficiency, directly affecting drive power consumption and signal quality. Accurately obtaining the actual half-wave voltage of the MZM and evaluating the difference between its upper and lower half-wave voltages is crucial for determining the chip's usability during the research and development and production of silicon photonics chips.

[0003] Currently, common methods for evaluating half-wave voltage mostly rely on measuring independent test structures in the wafer monitoring area and indirectly calculating the voltage. This approach has limitations: the test structures in the monitoring area cannot completely replicate the actual operating environment and process variations of the MZM inside the chip, so the test results often fail to accurately reflect the half-wave voltage performance of the MZM on the actual chip. Furthermore, conventional methods do not readily and conveniently measure the half-wave voltage of the upper and lower arms of the MZM separately, making it difficult to detect differences in the characteristics of the two arms in a timely manner. This could lead to some substandard chips being passed on to subsequent stages.

[0004] Therefore, it is essential to design a half-wave voltage testing method for silicon photonic chips. Summary of the Invention

[0005] The purpose of this invention is to provide a half-wave voltage testing method for silicon photonic chips. By converting electro-optic phase changes into spectral line shifts in the thermo-optic power domain, the half-wave voltage of each arm of the MZM on the chip can be measured in situ and independently, which helps to evaluate the differences between the upper and lower arms and improves the accuracy and practicality of the test.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for testing the half-wave voltage of a silicon photonics chip includes: Step 1: Acquire the first power spectral line and extract the free spectral range; Step 2: Acquire the second power spectral line; Step 3: Under the same coordinate system, read the displacement of the first power spectral line and the second power spectral line at the same power minimum point; Step 4: Calculate the phase change caused by the reverse bias based on the displacement and the free spectral range; Step 5: Calculate the half-wave voltage of the target measuring arm based on the phase change.

[0007] Further, in step 1, the first power spectral line is acquired, and the free spectral range is extracted, specifically as follows: Scan the voltage of any heater in the upper or lower arm, collect the first power spectrum line of the optical port power as the heater power changes, and extract the free spectral range from the first power spectrum line.

[0008] Furthermore, the free spectral range is determined based on the difference in heater power between two adjacent power minima on the first power spectral line.

[0009] Further, in step 2, the second power spectral line is acquired, specifically as follows: A known reverse bias voltage is applied to one of the target measurement arms of the MZM, and the voltage with the heater is scanned simultaneously to acquire a second power spectrum line in which the optical power at the optical port changes with the power of the heater.

[0010] Furthermore, in step 2, when the target measurement arm is the upper arm, the bias pad is connected to the positive bias, the RF positive terminal is shorted to the bias pad, and the RF negative terminal is grounded, and the reverse bias is applied only to the electro-optic modulator of the upper arm.

[0011] Furthermore, in step 2, when the target measurement arm is the lower arm, the bias pad is grounded, the Vcom pad is left floating, the positive RF terminal is shorted to the bias pad, the negative RF terminal is connected to the positive bias, and the reverse bias is applied only to the electro-optic modulator of the lower arm.

[0012] Furthermore, the forward bias voltage can be any one of 1V, 1.5V, 2V, or 3V.

[0013] Furthermore, in step 3, the displacement at the same power minimum point is the resonance valley point on the first power spectral line and the second power spectral line that is at the same interference order.

[0014] Further, in step 4, the phase change amount The calculation formula is: ; In the formula, is the displacement, and FSR is the free spectral range.

[0015] Furthermore, in step 5, the half-wave voltage of the target measuring arm The calculation formula is: ; In the formula, This represents the voltage change under reverse bias.

[0016] In summary, the present invention has the following beneficial technical effects: Firstly, it enables in-situ testing of the MZM on the chip, directly obtaining the half-wave voltage value under actual working conditions, reducing the deviation introduced by indirect calculation, and making the test results more reflective of the chip's true performance.

[0017] Secondly, by flexibly configuring the electrical path, reverse bias can be selectively applied to the upper or lower arm, thereby independently measuring the half-wave voltage of each arm and accurately determining the half-wave voltage difference between the two arms, providing an effective basis for evaluating the modulator symmetry and usability of the chip.

[0018] Third, this method uses a thermo-optical phase shifter as a tunable reference to convert the phase change caused by electro-optic modulation into the displacement of the spectral line on the heating power axis. The test process is controllable and the data processing is intuitive, with high test efficiency and operability.

[0019] It is understood that the above-mentioned beneficial effects come from multiple technical points of the present invention, including but not limited to the construction of interferometric spectral reference based on heater scanning, the specific electrical connection method of applying known reverse bias voltage to each arm of the MZM, and the algorithm steps for calculating half-wave voltage based on spectral shift and free spectral range. Attached Figure Description

[0020] Figure 1 For this purpose bright Test schematic diagram; Figure 2 For testing curves; Figure 3 For this purpose bright Method flowchart. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] This invention provides an embodiment of a method for testing the half-wave voltage of a silicon photonics chip. The silicon photonics chip addressed by this method includes a Mach-Zehnder modulator (MZM), which consists of an input terminal, a beam splitter, an upper arm, a lower arm, a beam combiner, and an output terminal. The upper and lower arms integrate a thermo-optical phase shifter (hereinafter referred to as a heater) for generating a thermo-optical effect to achieve phase modulation, and an electro-optical modulator for generating an electro-optical effect to achieve high-speed modulation. The chip also has corresponding electrode pads, including at least: a heating electrode pad for driving the heater, a bias pad for applying DC bias, a positive RF terminal (MZM RF+) and a negative RF terminal (MZM RF-) for inputting RF signals, and a common ground terminal (Vcom pad).

[0023] Figure 1 The diagram illustrates the testing principle upon which the testing method of this embodiment is based. Figure 2 The following is a set of test curves obtained by actual measurement using the method of this embodiment. Figure 3 This is a schematic diagram of the method flow of the present invention. The following will be combined with... Figure 1 , Figure 2 and Figure 3 The method for testing the half-wave voltage of the silicon photonics chip of the present invention will be described in detail. The method includes the following steps: Step 1: Acquire the first power spectral line and extract the free spectral range (FSR).

[0024] Specifically, scanning the voltage of any heater in the upper or lower arm—that is, changing the heating temperature by altering the applied electrical power—utilizes the thermo-optical effect to change the refractive index of the waveguide in that arm, thereby changing the phase of the optical signal transmitted through that arm. During the heater voltage scanning process, the optical power of the output light is collected in real time at the output port of the silicon photonics chip using an optical power meter or spectrometer. Plotting the heater power on the x-axis and the output port optical power on the y-axis yields the first power spectrum, such as... Figure 2 As shown by the blue dashed line, this first power spectral line exhibits periodic interference characteristics, manifested as a series of optical power maxima and minima.

[0025] The Free Spectral Range (FSR) is extracted from the obtained first power spectral line. In this embodiment, FSR is defined as the difference in heater power between two adjacent power minima (i.e., resonance troughs or dips). This difference corresponds to the effect introduced by the thermo-optical effect. Phase change over an entire cycle.

[0026] Step 2: Acquire the second power spectral line.

[0027] The purpose of this step is to apply a known reverse bias voltage to one of the target measurement arms of the MZM to introduce an additional phase difference through the electro-optic effect, and then scan the heater voltage again to obtain a second set of interference spectra. Specifically, this includes the following two sub-cases: Scenario 1: When the target measuring arm is the upper arm.

[0028] Connect a positive bias voltage to the bias pad (Vbias pad). This positive bias voltage can be any value from 1V, 1.5V, 2V, or 3V; this embodiment uses 1V as an example. Simultaneously, short-circuit the RF positive terminal (MZM RF+) to the bias pad (Vbias pad), so that the anode of the electro-optic modulator in the upper arm receives this positive bias voltage; ground the RF negative terminal (MZM RF-). This applies a reverse bias voltage of the selected positive bias value to the electro-optic modulator in the upper arm. Under this bias state, scan the voltage of the same heater as in step 1, and again acquire the spectral line showing the change in optical power from the port to the heater power; this is the second power spectral line. Figure 2 As shown by the orange dashed line.

[0029] Scenario 2: When the target measuring arm is the lower arm.

[0030] Ground the bias pad (Vbias pad) and leave the Vcom pad floating. Simultaneously, short-circuit the RF positive terminal (MZM RF+) to the bias pad (Vbias pad), thus grounding it as well; connect the RF negative terminal (MZM RF-) to a forward bias voltage, which can be any of 1V, 1.5V, 2V, or 3V; in this embodiment, 1V is used as an example. This gives the cathode of the lower arm's electro-optic modulator this forward bias voltage, while the anode is grounded, thus applying a reverse bias voltage of the selected forward bias value to the lower arm's electro-optic modulator. Under this bias state, scan the voltage of the same heater as in step 1, and again acquire the spectral line showing the change in optical power with heater power, similarly obtaining... Figure 2 The second power spectral line is shown by the orange dashed line in the middle.

[0031] With the above two electrical connection methods, reverse bias voltage can be applied independently to the electro-optic modulator of the upper or lower arm, thus laying the foundation for measuring the half-wave voltage of the upper and lower arms separately.

[0032] Step 3: Under the same coordinate system, read the displacement of the first power spectral line and the second power spectral line at the same power minimum point.

[0033] like Figure 2 As shown, the first power spectral line (blue dashed line) and the second power spectral line (orange dashed line) are plotted on the same coordinate system. It can be observed that, due to the application of a reverse bias voltage changing the initial phase of the target measuring arm, the second power spectral line is translated relative to the first power spectral line along the horizontal axis (heater power axis). In this step, the power minimum point (resonance valley) on the two spectral lines at the same interference order is selected, and the difference between the two on the heater power coordinate is read. This difference is the displacement, denoted as [missing value]. .

[0034] Step 4: Calculate the phase change caused by the reverse bias based on the displacement and the free spectral range.

[0035] As mentioned earlier, the free spectral range (FSR) corresponds to the heat generated by the heater. Phase change. Therefore, displacement. The ratio to FSR, multiplied by That is, the phase change introduced by the applied reverse bias voltage. The specific calculation formula is as follows: ; In the formula, Both FSR and FSR are units of heat power (e.g., milliwatts). The unit is radians. This formula is one of the core elements of the method of this invention, establishing a quantitative relationship between the spectral line shift and the optical phase change in the heater power domain.

[0036] Step 5: Calculate the half-wave voltage of the target measuring arm based on the phase change.

[0037] Half-wave voltage The definition is to enable the electro-optic modulator to produce The voltage value required for the radian phase change. In this step, the applied voltage change is known. (i.e., the magnitude of the reverse bias voltage, such as 1V or 3V), and the phase change corresponding to this voltage change is calculated through step 4. Then it can be obtained from the linear proportional relationship. The specific calculation formula is as follows: ; For example, when the applied reverse bias voltage When the value is 1V, the calculated value is... That is, the half-wave voltage value at the 1V bias operating point; when When the voltage is 3V, the calculated value is... This is the half-wave voltage value at the 3V operating point.

[0038] By using the upper arm as the target measurement arm (execution case one) and the lower arm as the target measurement arm (execution case two), and performing the complete steps 1 to 5 described above for each, the half-wave voltage of the upper arm and the half-wave voltage of the lower arm can be obtained respectively. Further calculation of the difference between the two allows for precise confirmation of the voltage characteristics of the upper and lower arms of the MZM. The differences are used to evaluate the modulation performance of the chip.

[0039] The testing method of this invention constructs a tunable interferometric reference using a thermo-optical phase shifter, converting the phase change caused by the electro-optic effect into a displacement of the spectral lines on the heater power axis, thus enabling the measurement of each arm of the MZM. In-situ, rapid, and accurate measurements effectively avoid the shortcomings of traditional wafer monitoring area tests that cannot reflect the true state of the chip, and can accurately quantify the asymmetry of the performance of the two arms.

[0040] Embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0041] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0042] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0043] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0044] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A method for testing the half-wave voltage of a silicon photonic chip, characterized in that, include: Step 1: Acquire the first power spectral line and extract the free spectral range; Step 2: Acquire the second power spectral line; Step 3: Under the same coordinate system, read the displacement of the first power spectral line and the second power spectral line at the same power minimum point; Step 4: Calculate the phase change caused by the reverse bias based on the displacement and the free spectral range; Step 5: Calculate the half-wave voltage of the target measuring arm based on the phase change.

2. The method for testing the half-wave voltage of a silicon photonic chip according to claim 1, characterized in that, In step 1, the first power spectral line is acquired, and the free spectral range is extracted, specifically as follows: Scan the voltage of any heater in the upper or lower arm, collect the first power spectrum line of the optical port power as the heater power changes, and extract the free spectral range from the first power spectrum line.

3. The method for testing the half-wave voltage of a silicon photonic chip according to claim 2, characterized in that, The free spectral range is determined based on the difference in heater power between two adjacent power minima on the first power spectral line.

4. The method for testing the half-wave voltage of a silicon photonic chip according to claim 1, characterized in that, In step 2, the second power spectral line is acquired, specifically as follows: A known reverse bias voltage is applied to one of the target measurement arms of the MZM, and the voltage with the heater is scanned simultaneously to acquire a second power spectrum line in which the optical power at the optical port changes with the power of the heater.

5. The method for testing the half-wave voltage of a silicon photonic chip according to claim 4, characterized in that, In step 2, when the target measurement arm is the upper arm, the bias pad is connected to the positive bias, the RF positive terminal is shorted to the bias pad, and the RF negative terminal is grounded. The reverse bias is applied only to the electro-optic modulator of the upper arm.

6. The method for testing the half-wave voltage of a silicon photonic chip according to claim 5, characterized in that, In step 2, when the target measurement arm is the lower arm, the bias pad is grounded, the Vcom pad is left floating, the RF positive terminal is shorted to the bias pad, the RF negative terminal is connected to the forward bias, and the reverse bias is applied only to the electro-optic modulator of the lower arm.

7. The method for testing the half-wave voltage of a silicon photonic chip according to claim 6, characterized in that, The forward bias voltage can be any one of 1V, 1.5V, 2V or 3V.

8. The method for testing the half-wave voltage of a silicon photonic chip according to claim 1, characterized in that, In step 3, the displacement at the same power minimum point is the resonance valley point on the first power spectral line and the second power spectral line that is at the same interference order.

9. The method for testing the half-wave voltage of a silicon photonic chip according to claim 1, characterized in that, In step 4, the phase change amount The calculation formula is: ； In the formula, is the displacement, and FSR is the free spectral range.

10. The method for testing the half-wave voltage of a silicon photonic chip according to claim 9, characterized in that, In step 5, the half-wave voltage of the target measuring arm The calculation formula is: ； In the formula, This represents the voltage change under reverse bias.

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