Equivalent circuit model of electro-absorption modulator and method for determining parameters thereof

Abstract

The application discloses an equivalent circuit model of an electro-absorption modulator and a parameter determination method thereof. The equivalent circuit model of the electro-absorption modulator adds a transverse leakage current module connected with a basic parasitic network, simulates an equivalent inductance effect generated by a transverse leakage current path in a ridge waveguide structure in an EAM device at high frequencies, and makes the equivalent inductance effect act together with path parasitic parameters to resonate at a specific frequency band and form corresponding recess characteristics on an S21 curve, so that high-frequency resonance and mismatch phenomena caused by the transverse leakage current are accurately characterized, the problem that an S21 curve recess at a 40-50 GHz frequency band cannot be reproduced due to neglect of the equivalent inductance characteristics in the related art is solved, and the accuracy of an EML high-frequency equivalent circuit model is improved.

Description

Technical Field

[0001] This application relates to the field of optical transmission, and in particular to an equivalent circuit model of an electroabsorption modulator and a method for determining its parameters. Background Technology

[0002] With the development of data centers and high-speed optical transmission networks, optical modules with speeds of 100G and above have become mainstream. This places higher demands on the high-frequency response characteristics of the electro-absorption modulated laser (EML), a core component. An EML integrates a laser and an electro-absorption modulator (EAM), with the EAM responsible for high-speed electro-optic modulation. Its high-frequency characteristics directly affect the overall bandwidth of the EML device. In high-frequency modeling of the EAM within an EML, current technologies generally only consider vertical carrier transport and parasitic parameters such as wire bonding in the packaging process.

[0003] However, actual measurements revealed that the traditional model could not reproduce the non-negligible roll-off phenomenon of the S21 curve in the 40-50 GHz band. This bandwidth limitation is closely related to the ridge waveguide structure of EAM, whose lateral leakage current path exhibits equivalent inductance characteristics at high frequencies, leading to additional resonance and mismatch. Since the traditional model ignores this equivalent inductance effect, it cannot accurately describe the high-frequency response of EML devices.

[0004] Therefore, how to provide a solution to the above-mentioned technical problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide an equivalent circuit model of an electroabsorption modulator and a method for determining its parameters, which solves the problem that related technologies cannot reproduce the S21 curve dip in the 40-50GHz band and improves the accuracy of the EML high-frequency equivalent circuit model.

[0006] To address the aforementioned technical problems, this application provides an equivalent circuit model of an electroabsorption modulator, comprising:

[0007] A basic parasitic network is used to simulate the vertical carrier transport effect in EAM devices, as well as the parasitic parameters introduced by the package.

[0008] A lateral leakage current module, connected to the basic parasitic network, is used to simulate the inductive effect generated by the lateral leakage current path inside the EAM device at high frequencies.

[0009] Optionally, the lateral leakage current path is formed in the ridge waveguide structure of the EAM device;

[0010] The lateral leakage current module includes a first resistor, a first inductor, and a first capacitor, wherein the first resistor, the first inductor, and the first capacitor are connected in series.

[0011] Optionally, the underlying parasitic network includes:

[0012] The first simulation module is used to simulate the vertical carrier transport effect of EAM devices;

[0013] The second simulation module is used to simulate parasitic parameters introduced by the package;

[0014] The first simulation module is connected to the second simulation module, the first end of the lateral leakage current module is connected to the common node between the first simulation module and the second simulation module, and the second end of the lateral leakage current module is grounded.

[0015] Optionally, the first analog module includes a second resistor, a third resistor, a second capacitor, and a second inductor, wherein:

[0016] The first end of the second resistor is connected to the common node, the second end of the second resistor is connected to the first end of the third resistor, the first end of the second capacitor and the first end of the output port respectively, the second end of the third resistor is connected to the first end of the second inductor, and the second ends of the second capacitor, the second end of the second inductor and the second end of the output port are all grounded.

[0017] Optionally, the second analog module includes a third inductor, a fourth inductor, a fifth inductor, a fourth resistor, a third capacitor, and a fourth capacitor, wherein:

[0018] The first end of the third inductor is connected to the first end of the input port. The second end of the third inductor is connected to the first end of the third capacitor and the first end of the fourth inductor. The second end of the fourth inductor, the first end of the fourth capacitor, and the first end of the fifth inductor are all connected to the common node. The second end of the fifth inductor is connected to the first end of the fourth resistor. The second ends of the third capacitor, the fourth capacitor, the fourth resistor, and the second end of the input port are all grounded.

[0019] This application also provides a method for determining the parameters of an equivalent circuit model of an electroabsorption modulator. The equivalent circuit model of the electroabsorption modulator includes a basic parasitic network and a lateral leakage current module. The lateral leakage current module includes a first resistor, a first inductor, and a first capacitor, wherein the first resistor, the first inductor, and the first capacitor are connected in series. The parameter determination method includes:

[0020] Obtain the voltage-current relationship of the electroabsorption modulator within a preset voltage range, and calculate the target resistance value of the first resistor based on the voltage-current relationship;

[0021] The target capacitance value of the first capacitor is determined based on the scattering parameter measurement results of the electroabsorption modulator.

[0022] The target capacitance value and the preset resonant frequency are used to obtain the target capacitance value of the first inductor.

[0023] Optionally, the voltage-current relationship of the electroabsorption modulator within a preset voltage range is obtained, and the target resistance value of the first resistor is calculated based on the voltage-current relationship, including:

[0024] The current measurement values ​​corresponding to multiple voltage points of the electroabsorption modulator within a preset voltage range are obtained, and a voltage-current correspondence is established based on the multiple voltage points and the corresponding current measurement values.

[0025] Based on the voltage-current relationship, the first resistance value of the electroabsorption modulator under the first bias state and the second resistance value under the second bias state are determined.

[0026] Calculate the target resistance value of the first resistor using the first resistance value and the second resistance value.

[0027] Optionally, using the first resistance value and the second resistance value, the target resistance value of the first resistor is calculated, including:

[0028] The target resistance value of the first resistor is calculated using the first relational formula, which is: ;

[0029] in, The first resistance value, This is the second resistance value. The target resistance value is given.

[0030] Optionally, the scattering parameter measurement results include the S11 parameter measurement results;

[0031] Determining the target capacitance value of the first capacitor based on the scattering parameter measurement results of the electroabsorption modulator includes:

[0032] Obtain the S11 parameter measurement results of the electroabsorption modulator within a preset frequency band range, and obtain a reference S11 curve based on the S11 parameter measurement results;

[0033] Within the preset frequency band range, the capacitance value of the first capacitor is adjusted for simulation, resulting in multiple simulated S11 curves;

[0034] The simulated S11 curves are compared with the reference S11 curve, and the capacitance value corresponding to the simulated S11 curve that meets the first preset error condition is taken as the target capacitance value of the first capacitor.

[0035] Optionally, the target capacitance value and a preset resonant frequency are used to obtain the target inductance value of the first inductor, including:

[0036] Obtain the S21 parameter measurement results of the electroabsorption modulator within a preset operating frequency band, and obtain a reference S21 curve based on the S21 parameter measurement results;

[0037] Based on the target capacitance value and the preset resonant frequency, the initial inductance value of the first inductor is calculated based on the resonance relationship.

[0038] Based on the initial inductance value, the inductance value of the first inductor is adjusted within a preset inductance value range for simulation, resulting in multiple simulated S21 curves;

[0039] The simulated S21 curves are compared with the reference S21 curve, and the inductance value corresponding to the simulated S21 curve that meets the second preset error condition is taken as the target inductance value of the first inductor.

[0040] As can be seen, this application adds a lateral leakage current module connected to the basic parasitic network to the equivalent circuit model of the electroabsorption modulator. This simulates the equivalent inductance effect generated by the lateral leakage current path in the ridge waveguide structure inside the EAM device at high frequencies. The module, together with the path parasitic parameters, resonates in a specific frequency band, forming a corresponding dip feature on the S21 curve. This accurately characterizes the high-frequency resonance and mismatch phenomenon caused by the lateral leakage current, solving the problem that related technologies cannot reproduce the dip of the S21 curve in the 40-50GHz band due to neglecting this equivalent inductance characteristic. This improves the accuracy of the EML high-frequency equivalent circuit model. Attached Figure Description

[0041] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A schematic diagram of the equivalent circuit model of an electroabsorption modulator provided in this application;

[0043] Figure 2 A schematic diagram of the equivalent circuit model of another electroabsorption modulator provided in this application;

[0044] Figure 3 A flowchart illustrating the steps of a method for determining parameters of an equivalent circuit model of an electroabsorption modulator provided in this application;

[0045] Figure 4 A comparative schematic diagram of the first S11 curve provided in this application;

[0046] Figure 5 A comparative schematic diagram of the first S21 curve provided in this application;

[0047] Figure 6 A comparative diagram of the second type of S11 curve provided in this application;

[0048] Figure 7 A comparative diagram of the third type of S11 curve provided in this application;

[0049] Figure 8 A comparative schematic diagram of the second type of S21 curve provided in this application;

[0050] Figure 9 A comparative diagram of the third type of S21 curve provided in this application;

[0051] Figure 10 A comparative diagram of the fourth type of S11 curve provided in this application;

[0052] Figure 11 A comparative diagram of the fifth type of S11 curve provided in this application. Detailed Implementation

[0053] The core of this application is to provide an equivalent circuit model of an electroabsorption modulator and a method for determining its parameters, which solves the problem that related technologies cannot reproduce the S21 curve dip in the 40-50GHz band and improves the accuracy of the EML high-frequency equivalent circuit model.

[0054] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0055] Firstly, please refer to Figure 1 This application provides an equivalent circuit model of an electroabsorption modulator, including:

[0056] A basic parasitic network is used to simulate the vertical carrier transport effect in EAM devices, as well as the parasitic parameters introduced by the package.

[0057] The lateral leakage current module, connected to the basic parasitic network, is used to simulate the inductive effect generated by the lateral leakage current path inside the EAM device at high frequencies.

[0058] In this embodiment, the EAM equivalent circuit model is constructed from at least a basic parasitic network and a lateral leakage current module. The basic parasitic network is a collection of circuits used to simulate various effects inherent to the EAM device itself and those introduced by the package. Specifically, the basic parasitic network performs two functions: first, it simulates the carrier transport response of the EAM device in the vertical direction, which corresponds to the intrinsic characteristics of the active region of the EAM device, manifested as the vertical transport path formed by the capacitance and series resistance of the main PN junction; second, it simulates parasitic parameters introduced by the package, such as wire bonding inductance, pad-to-ground parasitic capacitance, etc., forming an external parasitic network.

[0059] Considering that the EAM equivalent circuit model built based on related technologies lacks characterization of the lateral leakage mechanism of the ridge waveguide sidewalls, resulting in an unexplained roll-off in the S21 curve in the 40-50GHz frequency band, this roll-off characteristic cannot be reproduced by the function simulated solely by the basic parasitic network. Therefore, this embodiment also incorporates a lateral leakage current module when building the EAM equivalent circuit model. One end of this lateral leakage current module is connected to a specific node in the basic parasitic network, and the other end is grounded, thus forming a signal leakage path in parallel with the main vertical transmission path. It is understood that the lateral leakage current module is configured to simulate the electrical characteristics of the lateral leakage current path in the ridge waveguide structure, especially the inductive characteristics of the lateral leakage current path at high frequencies. When the operating frequency enters the 40-50GHz band, the lateral leakage current path resonates and couples with the capacitive component in the circuit due to the inductive effect. This leads to an enhanced bypass effect of the signal leakage path on the signal in this band, causing some high-frequency signal energy to no longer be transmitted completely along the main vertical transmission path, but to leak to ground through the signal leakage path. This results in an amplitude drop on the S21 curve of the main vertical transmission path, thus enabling the equivalent circuit model of the electroabsorption modulator built in this application to accurately reproduce the dip phenomenon of the S21 curve in a specific frequency band.

[0060] The equivalent circuit model of the electroabsorption modulator constructed in this embodiment can achieve accurate simulation and prediction of the high-frequency characteristics of the device, thereby guiding the optimized design of the electroabsorption modulator and its integrated components (such as EML) or packaging structure (such as COC), effectively suppressing high-frequency signal dips and improving the operating bandwidth of the device.

[0061] Please refer to Figure 2 The equivalent circuit model of the electroabsorption modulator provided in this application is based on the above embodiments:

[0062] In one exemplary embodiment, a lateral leakage current path is formed in the ridge waveguide structure of the EAM device;

[0063] The lateral leakage current module includes a first resistor R1, a first inductor L1, and a first capacitor C1, wherein the first resistor R1, the first inductor L1, and the first capacitor C1 are connected in series.

[0064] It is understandable that in existing ridge waveguide EAM devices, in addition to the main vertical carrier transport, a portion of carriers also leak laterally along the sidewalls or substrate of the ridge waveguide. This lateral leakage current exhibits a significant inductive effect at high frequencies and forms a resonant circuit with parasitic capacitance, resulting in an abnormal dip in the S21 curve at specific frequency bands (such as around 42 GHz). Based on this, the lateral leakage current module in this application is mainly used to simulate the lateral leakage current path formed in the ridge waveguide structure of the EAM device.

[0065] Specifically, the lateral leakage current module includes a first resistor R1, a first inductor L1, and a first capacitor C1. These three components are connected in series to form a complete RLC series branch. In one feasible connection topology, one end of the first resistor R1 is connected to a common node, and the other end is connected in series with the first inductor L1 and the first capacitor C1, with the end of the first capacitor C1 grounded. Of course, the series order of the first resistor R1, the first inductor L1, and the first capacitor C1 in the branch can be interchanged, as long as the three together form a series branch and are connected between the common node and ground. In this RLC series branch, the first resistor R1 is used to characterize the ohmic loss and scattering loss on the lateral leakage current path, the first inductor L1 is used to characterize the inductive effect generated by the lateral leakage current path at high frequencies, and the first capacitor C1 is used to characterize the coupling capacitance or barrier capacitance in the lateral leakage current path. At a specific frequency, the first inductor L1 and the first capacitor C1 will resonate in series, minimizing the impedance of the lateral leakage current module (mainly determined by the first resistor R1), thereby providing a low-impedance leakage path for high-frequency signals. At this point, the high-frequency signal is diverted to ground through this channel, causing a significant amplitude drop, or dip, in the S21 curve of the main vertical transmission path at this frequency point.

[0066] This embodiment constructs a lateral leakage current module comprising a first resistor R1, a first inductor L1, and a first capacitor C1 connected in series. This not only reproduces the physical path of the lateral leakage current on the sidewall of the ridge waveguide from a circuit topology perspective, but more importantly, it utilizes the series resonance mechanism to achieve the reproduction and decoupling control of the S21 curve dip phenomenon in the 40-50GHz frequency band. Specifically, the first resistor R1 independently controls the depth of the dip in the S21 curve, while the first inductor L1 and the first capacitor C1 jointly control the frequency position where the S21 curve dip occurs.

[0067] In one exemplary embodiment, the basic parasitic network includes:

[0068] The first simulation module is used to simulate the vertical carrier transport effect of EAM devices;

[0069] The second simulation module is used to simulate parasitic parameters introduced by the package;

[0070] The first simulation module is connected to the second simulation module, the first end of the lateral leakage current module is connected to the common node between the first simulation module and the second simulation module, and the second end of the lateral leakage current module is grounded.

[0071] In this embodiment, the basic parasitic network is divided into a first simulation module and a second simulation module based on its specific functional implementation. The first simulation module is used to simulate the vertical carrier transport effect of the EAM device, i.e., the intrinsic characteristics of the active region of the device. Specifically, at the physical level, when the electroabsorption modulator is working, the carriers mainly move in the vertical direction of the PN junction to generate the electroabsorption effect. The first simulation module uses series resistors, inductors, and parallel capacitors to represent the junction resistance loss, depletion layer capacitance effect, and vertical propagation delay in this process. The second simulation module is used to simulate parasitic parameters introduced by the package, such as wire bonding inductance and pad capacitance. Specifically, in actual devices, the chip needs to be connected to external circuits through wire bonding, pads, and pins. These structures introduce non-negligible parasitic inductance and capacitance. The second simulation module is a circuit abstraction of these non-ideal packaging effects. The first and second simulation modules are connected to each other in sequence to form the main architecture of the main vertical propagation path, while the lateral leakage current module is connected to the main vertical propagation path as a bypass branch. Specifically, the first end of the lateral leakage current module is connected to the common node between the first and second analog modules. This common node physically corresponds to the connection node between the active region of the electroabsorption modulator and the package structure. The second end of the lateral leakage current module is directly grounded. This connection allows the lateral leakage current module to be connected in parallel across the intrinsic model of the active region and the external parasitic network, thus clearly distinguishing the three independent physical processes of vertical carrier transport effect, external package parasitic effect, and lateral leakage effect in the circuit structure. The structure of this embodiment realizes independent modeling and parameter determination of the intrinsic characteristics of the device and the parasitic parameters of the package, avoiding parameter coupling interference between different physical effects. At the same time, connecting the lateral leakage current module to the boundary node between the active region and the package conforms to the actual physical location of the lateral leakage current in the ridge waveguide structure, ensuring the authenticity of the high-frequency signal bypass path. Furthermore, this topology allows the lateral leakage current module to be activated only at high frequencies due to the resonance effect, while exhibiting high impedance at low frequencies and in DC conditions without affecting the normal operation of the main vertical transmission path. Thus, while ensuring the simulation accuracy across the entire frequency band, it solves the problem of the inability to reproduce the S21 curve concavity in the 40-50GHz band.

[0072] In an exemplary embodiment, the first analog module includes a second resistor R2, a third resistor R3, a second capacitor C2, and a second inductor L2, wherein:

[0073] The first end of the second resistor R2 is connected to the common node. The second end of the second resistor R2 is connected to the first end of the third resistor R3, the first end of the second capacitor C2, and the first end of the output port P2. The second end of the third resistor R3 is connected to the first end of the second inductor L2. The second ends of the second capacitor C2, the second end of the second inductor L2, and the second end of the output port P2 are all grounded.

[0074] In this embodiment, the first simulation module specifically includes a second resistor R2, a third resistor R3, a second capacitor C2, and a second inductor L2. In the connection topology, the second resistor R2 serves as an input stage component, with its first end connected to a common node (i.e., the connection point with the lateral leakage current module), and its second end acting as a key shunt node, connected to the first end of the third resistor R3, the first end of the second capacitor C2, and the first end of the output port P2. Subsequently, the third resistor R3 and the second inductor L2 are connected in series and then grounded; that is, the second end of the third resistor R3 is connected to the first end of the second inductor L2, the second end of the second inductor L2 is grounded, and the other end of the second capacitor C2 is directly grounded. The second end of the output port P2 is also grounded. In this series-parallel hybrid structure, the second resistor R2 simulates the series resistance of the main PN junction in the active region, the second capacitor C2 simulates the depletion layer capacitance of the main PN junction, and the series branch of the third resistor R3 and the second inductor L2 simulates the dynamic response and parasitic inductance effect of charge carriers during vertical transport in the active region. This topology can accurately fit the impedance characteristics of the electroabsorption modulator in the low to mid frequency range, providing an accurate benchmark model for high-frequency resonance analysis.

[0075] In an exemplary embodiment, the second analog module includes a third inductor L3, a fourth inductor L4, a fifth inductor L5, a fourth resistor R4, a third capacitor C3, and a fourth capacitor C4, wherein:

[0076] The first end of the third inductor L3 is connected to the first end of the input port P1. The second end of the third inductor L3 is connected to the first end of the third capacitor C3 and the first end of the fourth inductor L4. The second end of the fourth inductor L4, the first end of the fourth capacitor C4, and the first end of the fifth inductor L5 are all connected to a common node. The second end of the fifth inductor L5 is connected to the first end of the fourth resistor R4. The second ends of the third capacitor C3, the fourth capacitor C4, the fourth resistor R4, and the second end of the input port P1 are all grounded.

[0077] In this embodiment, the second simulation module is used to simulate a complex packaging environment, including a third inductor L3, a fourth inductor L4, a fifth inductor L5, a fourth resistor R4, a third capacitor C3, and a fourth capacitor C4. In the specific circuit connection, the signal enters from the input port P1, first passing through the third inductor L3, which serves as the equivalent of wire bonding at the input stage. Its output is connected to the third capacitor C3, which serves as the parasitic capacitance to ground at the input stage, and the fourth inductor L4, which serves as the intermediate stage connection. The other end of the third capacitor C3 is grounded. The signal is transmitted to the common node via the fourth inductor L4. At the same time, one end of the fourth capacitor C4, which serves as another parasitic coupling path, is also connected to this common node. In addition, the fifth inductor L5 and the fourth resistor R4 are connected in series and then grounded, forming a loss loop at the bottom of the package. Finally, the other ends of the third capacitor C3, the fourth capacitor C4, the fourth resistor R4, and the second end of the input port P1 are all grounded. Through this network composed of multiple levels of inductors, capacitors, and resistors, this embodiment can simulate the wire bonding inductance, pad-to-ground capacitance, substrate transmission line loss, and coupling effects between pins generated during the packaging process. This high-precision packaging modeling ensures that the input reflection coefficient (S11) of the equivalent circuit in the low-frequency band matches the measured data, eliminating the interference of packaging parasitic parameters on the extraction of active region intrinsic parameters and transverse leakage current parameters, thereby guaranteeing the simulation confidence of the entire electroabsorption modulator equivalent circuit model across the entire frequency band.

[0078] Please refer to Figure 3 This application also provides a method for determining the parameters of an equivalent circuit model of an electroabsorption modulator. The equivalent circuit model of the electroabsorption modulator includes a basic parasitic network and a lateral leakage current module. The lateral leakage current module includes a first resistor, a first inductor, and a first capacitor, wherein the first resistor, the first inductor, and the first capacitor are connected in series. The parameter determination method includes:

[0079] S101: Obtain the voltage-current relationship of the electroabsorption modulator within a preset voltage range, and calculate the target resistance value of the first resistor based on the voltage-current relationship;

[0080] Specifically, based on the circuit structure described above, this embodiment provides a parameter determination method that solves the problems of severe parameter coupling and difficulty in fitting in traditional modeling.

[0081] First, this application obtains the voltage-current relationship of the point absorption modulator within a preset voltage range. This preset voltage range covers the entire range of the device from zero bias to normal operating bias (e.g., 0V to the negative bias region). The voltage-current relationship refers to the DC-IV characteristic curve continuously scanned and measured within this preset voltage range. This voltage-current relationship is the physical basis for calculating the target resistance value of the first resistor. Since the first resistor in the lateral leakage current module mainly characterizes the ohmic characteristics of the internal leakage current path of the device, its resistance value directly reflects the changing trend of the overall DC conductivity behavior of the device. Therefore, by analyzing the nonlinear conduction characteristics presented by the voltage-current relationship, the target resistance value of the first resistor characterizing the impedance characteristics of this lateral leakage current path can be derived without relying on complex high-frequency iterations.

[0082] This method of determining resistance parameters directly based on DC test data effectively utilizes the physical mechanism that lateral leakage current is sensitive to bias voltage, decoupling the process of extracting resistance parameters from high-frequency resonant parameters. It avoids the convergence difficulties caused by the entanglement of resistance with other component parameters in traditional fitting, and significantly improves the initial accuracy of parameter configuration.

[0083] S102: Determine the target capacitance value of the first capacitor based on the scattering parameter measurement results of the electroabsorption modulator.

[0084] Specifically, before performing this step, a Vector Network Analyzer (VNA) test is required to obtain the scattering parameter measurement results of the electroabsorption modulator. Accordingly, the scattering parameter measurement results mainly include the S11 parameter (input reflection coefficient) curves in the low-frequency band (e.g., 0 GHz to 20 GHz). Since the series inductance in the lateral leakage current module is extremely small in the low-frequency range and does not exhibit obvious resonant characteristics, the lateral leakage current module mainly exhibits capacitive impedance characteristics. At this time, the circuit's input reflection characteristics are sensitive to changes in the capacitance value. Therefore, by comparing and fitting the simulated model's S11 response in this low-frequency band with the measured scattering parameter results, the target capacitance value of the first capacitor can be determined. This step utilizes frequency band isolation to effectively avoid interference from high-frequency resonant points on capacitor extraction, ensuring the independence and accuracy of the capacitor parameters and providing a reliable benchmark for subsequent inductance value calculation.

[0085] S103: Using the target capacitance value and the preset resonant frequency, the target capacitance value of the first inductor is obtained.

[0086] In this embodiment, the preset resonant frequency refers to the center frequency point (e.g., 42GHz) where the amplitude dips in the S21 curve of the electroabsorption modulator occurs in the 40GHz to 50GHz frequency band. This frequency point corresponds to the characteristic frequency at which the lateral leakage current module experiences series resonance. Based on the determined target capacitance value, the preset resonant frequency, and the LC series resonance equation, the target inductance value of the first inductor can be directly calculated. The LC series resonance equation is as follows: .

[0087] This application adopts the order of determining the resistor and capacitor first and then the inductor, which avoids the local convergence problem in traditional multi-parameter joint optimization and improves the efficiency and accuracy of parameter determination.

[0088] In one exemplary embodiment, obtaining the voltage-current correspondence of the electroabsorption modulator within a preset voltage range, and calculating the target resistance value of the first resistor based on the voltage-current correspondence, includes:

[0089] Acquire the current measurement values ​​corresponding to multiple voltage points of the electroabsorption modulator within a preset voltage range, and establish the voltage-current correspondence based on the multiple voltage points and their corresponding current measurement values;

[0090] Based on the relationship between voltage and current, the first resistance value of the electroabsorption modulator under the first bias state and the second resistance value under the second bias state are determined.

[0091] Calculate the target resistance value of the first resistor using the first resistance value and the second resistance value;

[0092] The target resistance value of the first resistor is calculated using the first relational formula, which is: ;in, The first resistance value, This is the second resistance value. The target resistance value is defined as follows. In this embodiment, multiple voltage points within a preset voltage range are discrete sampling points uniformly distributed according to a preset step value (e.g., 0.1V). If the preset voltage range is set to 0V to -4V, then the multiple voltage points specifically cover a series of test points from 0V, -0.1V, -0.2V... up to -4V. After determining these discrete voltage points, the current measurement value corresponding to the electroabsorption modulator at each discrete voltage point is obtained point by point using a DC parameter tester. These discrete data points are then fitted to construct a continuous and smooth voltage-current correspondence curve (i.e., the DC IV characteristic curve).

[0093] Subsequently, from the constructed voltage-current relationship curves, two bias states that reflect the difference in lateral leakage current characteristics were selected as feature points, namely the first bias state and the second bias state. In the first bias state, the internal electric field of the device is relatively weak, and the lateral leakage path exhibits low impedance characteristics. The second bias state is selected as the negative bias state (e.g., -2V) when the electroabsorption modulator is operating normally, at which point the impedance of the lateral leakage path changes significantly. The dynamic resistance values ​​in these two states are calculated to obtain the first resistance value. Second resistance value .

[0094] Finally, using the specific mathematical relationship between these two resistance values, namely the first relationship in this embodiment... To calculate the target resistance value of the first resistor, it is understandable. The magnitude of the current affects the depth of the indentation. This embodiment utilizes the physical characteristic that the resistance of the lateral leakage current changes significantly under different bias voltages, so that the extraction of the target resistance value of the first resistor depends entirely on the DC IV test data, without relying on complex high-frequency simulation iterations, thus ensuring the accuracy of parameter determination.

[0095] In one exemplary embodiment, the scattering parameter measurement results include the S11 parameter measurement results;

[0096] Based on the scattering parameter measurement results of the electroabsorption modulator, the target capacitance value of the first capacitor is determined, including:

[0097] Obtain the S11 parameter measurement results of the electroabsorption modulator within a preset frequency band, and obtain the reference S11 curve based on the S11 parameter measurement results;

[0098] Within a preset frequency band, the capacitance value of the first capacitor is adjusted for simulation, resulting in multiple simulated S11 curves.

[0099] Multiple simulated S11 curves are compared with a reference S11 curve, and the capacitance value corresponding to the simulated S11 curve that meets the first preset error condition is taken as the target capacitance value of the first capacitor.

[0100] In this embodiment, the scattering parameter measurement results specifically include the S11 parameter measurement results in the low-frequency band (e.g., 0 GHz to 20 GHz). The S11 parameter characterizes the reflection coefficient of the signal reflected back from the input port, directly reflecting the matching degree between the input impedance of the electro-absorption modulator and the system reference impedance. In the low-frequency range, the series inductor reactance in the lateral leakage current module is extremely small, and no significant resonance effect has yet formed. This results in the signal leakage path exhibiting a purely capacitive characteristic dominated by the first capacitor. At this point, the shape of the S11 curve is extremely sensitive to changes in the capacitance value of the first capacitor; even a small adjustment in the capacitance value can cause a significant shift in the S11 curve, and it is almost unaffected by interference from other high-frequency parasitic parameters. Based on the aforementioned low-frequency capacitive dominance physical characteristics, this embodiment selects the S11 parameter as the basis for determining the target capacitance value of the first capacitor.

[0101] The preset frequency band is preferably set to 0 GHz to 20 GHz. This band can fully reflect the influence of the capacitor on the input reflection characteristics and effectively isolate the complex fluctuations caused by the resonance of the transverse leakage current module above 40 GHz. During measurement, a vector network analyzer is used to record the S11 parameter measurement data corresponding to each frequency point in frequency sweep mode. After obtaining the raw measurement data, a continuous and smooth reference S11 curve is constructed based on the S11 parameter measurement results through data interpolation or fitting processing to eliminate test noise and serve as a benchmark for subsequent comparisons.

[0102] Within the aforementioned preset frequency band range, and within a preset capacitance range (e.g., 0.01pF to 0.1pF), the capacitance value of the first capacitor is adjusted to perform circuit simulation, resulting in multiple simulated S11 curves corresponding to different capacitance values.

[0103] Then, multiple simulated S11 curves need to be compared with a reference S11 curve. The capacitance value corresponding to the simulated S11 curve that meets the first preset error condition is taken as the target capacitance value of the first capacitor. Figure 4 As shown. The first preset error condition here can be a quantitative standard, such as the root mean square error between two curves being less than a certain threshold, or the deviation at certain key frequency points being within the allowable range. The comparison process can be done manually by observation and judgment, or it can be completed automatically by an optimization algorithm. After finding the simulation curve that meets the error condition, the capacitance value corresponding to that curve is determined as the target capacitance value.

[0104] In one exemplary embodiment, obtaining the target capacitance value of the first inductor using the target capacitance value and a preset resonant frequency includes:

[0105] Obtain the S21 parameter measurement results of the electroabsorption modulator within the preset operating frequency band, and obtain the reference S21 curve based on the S21 parameter measurement results;

[0106] Based on the target capacitance value and the preset resonant frequency, the initial inductance value of the first inductor is calculated according to the resonant relationship.

[0107] Based on the initial inductance value, the inductance value of the first inductor was adjusted within the preset inductance value range for simulation, resulting in multiple simulated S21 curves;

[0108] Multiple simulated S21 curves are compared with a reference S21 curve, and the inductance value corresponding to the simulated S21 curve that meets the second preset error condition is taken as the target inductance value of the first inductor.

[0109] In this embodiment, the S21 parameter measurement results of the electroabsorption modulator within a preset operating frequency band are first obtained, and a reference S21 curve is obtained based on these measurement results. The S21 parameter here characterizes the signal transmission characteristics from the input port to the output port. Within this preset operating frequency band, due to the series resonance effect of the lateral leakage current module, a significant amplitude dip will appear on the reference S21 curve. In this embodiment, the center frequency at this dip is extracted and defined as the preset resonant frequency, which directly corresponds to the physical state of series resonance of the lateral leakage current module.

[0110] Then, based on the LC series resonance relationship... The initial inductance value of the first inductor can be directly calculated, providing a theoretical approximation of the inductance parameters and quickly narrowing the search range to near the true value. This embodiment further considers that the resonant frequency in actual circuits is affected by other parasitic parameters, and the initial value calculated solely from the LC series resonance equation may not perfectly match the position and shape of the concave curve in the simulated S21 curve with the measured curve. Therefore, this embodiment uses the initial inductance value as a benchmark and adjusts the inductance value of the first inductor within a preset inductance value range for simulation, obtaining multiple simulated S21 curves. The preset inductance value range is empirically set to 0.1nH to 1nH, covering most practically feasible inductance values.

[0111] Finally, multiple simulated S21 curves are compared with a reference S21 curve. The inductance value corresponding to the simulated S21 curve that meets the second preset error condition is taken as the target inductance value of the first inductor. Figure 5 As shown. The second preset error condition here can include multiple aspects, such as the degree of matching of the concave frequency, the degree of matching of the concave depth, and the similarity of the overall shape of the curve. After finding the best matching simulation curve, the inductance value corresponding to that curve is the final determined target inductance value. This embodiment utilizes the LC resonance formula to quickly approximate the correct value, and eliminates the deviation caused by model simplification and measurement errors through simulation fitting, ensuring the accuracy of parameter determination.

[0112] Furthermore, this embodiment also verifies the correctness of the model by changing the resistance value of the second resistor in the EAM model. Changing the resistance value of the second resistor, the simulation results and the measured results show the same trend, further verifying the correctness of the model. (Refer to...) Figure 6 and Figure 7 As shown. Furthermore, this embodiment also verifies the correctness of the model by changing the resistance value of the fourth resistor in the EAM model. Changing the resistance value of the fourth resistor, the simulation results and the measured results show the same trend, further verifying the correctness of the model. (Refer to...) Figures 8 to 11 As shown.

[0113] In summary, the optimized model of this application more accurately matches the measured data and can be adapted to high-speed EML devices with different packaging forms, providing more reliable simulation results for subsequent device optimization. It should also be noted that in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0114] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An equivalent circuit model of an electroabsorption modulator, characterized in that, include: A basic parasitic network is used to simulate the vertical carrier transport effect in EAM devices, as well as the parasitic parameters introduced by the package. A lateral leakage current module, connected to the basic parasitic network, is used to simulate the inductive effect generated by the lateral leakage current path inside the EAM device at high frequencies.

2. The equivalent circuit model of the electroabsorption modulator according to claim 1, characterized in that, The lateral leakage current path is formed in the ridge waveguide structure of the EAM device; The lateral leakage current module includes a first resistor, a first inductor, and a first capacitor, wherein the first resistor, the first inductor, and the first capacitor are connected in series.

3. The equivalent circuit model of the electroabsorption modulator according to claim 1, characterized in that, The underlying parasitic network includes: The first simulation module is used to simulate the vertical carrier transport effect of EAM devices; The second simulation module is used to simulate parasitic parameters introduced by the package; The first simulation module is connected to the second simulation module, the first end of the lateral leakage current module is connected to the common node between the first simulation module and the second simulation module, and the second end of the lateral leakage current module is grounded.

4. The equivalent circuit model of the electroabsorption modulator according to claim 3, characterized in that, The first analog module includes a second resistor, a third resistor, a second capacitor, and a second inductor, wherein: The first end of the second resistor is connected to the common node, the second end of the second resistor is connected to the first end of the third resistor, the first end of the second capacitor and the first end of the output port respectively, the second end of the third resistor is connected to the first end of the second inductor, and the second ends of the second capacitor, the second end of the second inductor and the second end of the output port are all grounded.

5. The equivalent circuit model of the electroabsorption modulator according to claim 4, characterized in that, The second analog module includes a third inductor, a fourth inductor, a fifth inductor, a fourth resistor, a third capacitor, and a fourth capacitor, wherein: The first end of the third inductor is connected to the first end of the input port. The second end of the third inductor is connected to the first end of the third capacitor and the first end of the fourth inductor. The second end of the fourth inductor, the first end of the fourth capacitor, and the first end of the fifth inductor are all connected to the common node. The second end of the fifth inductor is connected to the first end of the fourth resistor. The second ends of the third capacitor, the fourth capacitor, the fourth resistor, and the second end of the input port are all grounded.

6. A method for determining the parameters of an equivalent circuit model of an electroabsorption modulator, characterized in that, The equivalent circuit model of the electroabsorption modulator includes a basic parasitic network and a lateral leakage current module. The lateral leakage current module includes a first resistor, a first inductor, and a first capacitor, wherein the first resistor, the first inductor, and the first capacitor are connected in series. The parameter determination method includes: Obtain the voltage-current relationship of the electroabsorption modulator within a preset voltage range, and calculate the target resistance value of the first resistor based on the voltage-current relationship; The target capacitance value of the first capacitor is determined based on the scattering parameter measurement results of the electroabsorption modulator. The target capacitance value and the preset resonant frequency are used to obtain the target capacitance value of the first inductor.

7. The method for determining the parameters of the equivalent circuit model of the electroabsorption modulator according to claim 6, characterized in that, Obtaining the voltage-current relationship of the electroabsorption modulator within a preset voltage range, and calculating the target resistance value of the first resistor based on the voltage-current relationship, includes: The current measurement values ​​corresponding to multiple voltage points of the electroabsorption modulator within a preset voltage range are obtained, and a voltage-current correspondence is established based on the multiple voltage points and the corresponding current measurement values. Based on the voltage-current relationship, the first resistance value of the electroabsorption modulator under the first bias state and the second resistance value under the second bias state are determined. Calculate the target resistance value of the first resistor using the first resistance value and the second resistance value.

8. The method for determining the parameters of the equivalent circuit model of the electroabsorption modulator according to claim 7, characterized in that, Using the first resistance value and the second resistance value, the target resistance value of the first resistor is calculated, including: The target resistance value of the first resistor is calculated using the first relational formula, which is: ; in, The first resistance value, This is the second resistance value. The target resistance value is given.

9. The method for determining the parameters of the equivalent circuit model of the electroabsorption modulator according to claim 6, characterized in that, The scattering parameter measurement results include the S11 parameter measurement results; Determining the target capacitance value of the first capacitor based on the scattering parameter measurement results of the electroabsorption modulator includes: Obtain the S11 parameter measurement results of the electroabsorption modulator within a preset frequency band range, and obtain a reference S11 curve based on the S11 parameter measurement results; Within the preset frequency band range, the capacitance value of the first capacitor is adjusted for simulation, resulting in multiple simulated S11 curves; The simulated S11 curves are compared with the reference S11 curve, and the capacitance value corresponding to the simulated S11 curve that meets the first preset error condition is taken as the target capacitance value of the first capacitor.

10. The method for determining the parameters of the equivalent circuit model of the electroabsorption modulator according to claim 9, characterized in that, Using the target capacitance value and the preset resonant frequency, the target inductance value of the first inductor is obtained, including: Obtain the S21 parameter measurement results of the electroabsorption modulator within a preset operating frequency band, and obtain a reference S21 curve based on the S21 parameter measurement results; Based on the target capacitance value and the preset resonant frequency, the initial inductance value of the first inductor is calculated based on the resonant relationship. Based on the initial inductance value, the inductance value of the first inductor is adjusted within a preset inductance value range for simulation, resulting in multiple simulated S21 curves; The simulated S21 curves are compared with the reference S21 curve, and the inductance value corresponding to the simulated S21 curve that meets the second preset error condition is taken as the target inductance value of the first inductor.

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