The ring_modulator photonic model is specifically tailored to modelling ring modulator active elements. It provides a method of creating both single-bus and double-bus ring modulators, which accurately model electrical and thermal modulation. This model can also create ring resonators without electrical and/or thermal modulation, and supports fine-tuning of model properties to match figures of merit.
When building a passive ring resonator using this model, the user simply has to skip providing some of the parameters specific to the active part of a ring modulator and CML Compiler will automatically turn the compact model into a passive ring. See below for more details on which parameter values to skip when creating a ring resonator model.
The ring_modulator photonic model supports statistical modeling. Users can choose an arbitrary number of statistical parameters and define their influence on the effective and group index of the ring as well as the resonant wavelength, insertion loss, free-spectral range, quality factor, and modulation efficiency of the modulator. For information on statistical CMLs, see Statistical CMLs.
In addition, the model supports linking its figures of merit together (a nominal to another nominal and a nominal to statistical) through a lookup table. If you happen to have multiple data points for various figures of merit, you can provide all the data points to the model and link them together so that for example, if a specific value was selected for quality factor (Q), a corresponding value for extinction ratio (ER) will be selected automatically by the model based on the data in the lookup table and ER can’t be set independent of the Q. This will enable you to limit the users of your model to the design space that is practical for you and avoid them of coming up with solutions that are impossible to fabricate. For more information about how to provide the data as a lookup table for FOMs, please see the Data File details for various ring templates.
Lumfoundry Templates: Ring Modulator, Ring Modulator (Statistical), Ring Resonator, Ring Resonator (Statistical)
Quality Assurance Test: ring_modulator QA
Statistical Modeling Support: Yes
Supported Parameters: None
Tuning Support: Resonant Wavelength, Free Spectral Range, Resonance Peak Shape ( IL at through and drop port, ER, Q), Electrical and Thermal Modulation Efficiency.
Interoperability with Cadence Virtuoso:
- Circuit design flows using INTERCONNECT model: Yes.
- Circuit design flow using photonic Verilog-A model: Yes (not for statistical models).
Advanced Options
The model is very versatile, and has several different options that can be enabled or disabled using different parameters included in the model data requirement. To see the list of data requirement please visit lumfoundry template pages.
Modulator/resonator model |
Modulator: ele_an and ele_cat ports exist resonator: ele_an and ele_cat ports do not exist |
Enable/disable thermally tuned model |
Enable: th_neg and th_pos ports exists Disable th_neg and th_pos ports do not exist |
Single/double bus |
Single Bus: opt_3 and opt_4 do not exist Double Bus: opt_3 and opt_4 exist |
Statistical/nominal model |
Statistical model: statistical section exist Nominal model: statistical section does not exist |
Model Information
- This model assumes thermal bandwidth to be constant over all bias range.
- This model only supports single mode operation.
- This model does not support ring radius as a parameter.
- The main required data to build a ring modulator model are summarized below.
Main required data |
Ring radius, length of each waveguide section. |
Effective index of each waveguide section. Insertion loss. Group index of each waveguide section. OR FSR. Loss of each waveguide section. Quality factor. Coupling coefficients. Extinction ratio. Resonant wavelength. |
Delta effective index (Re and Im) OR Electrical modulation efficiency. vs electrical tuner bias voltage |
Delta phase vs thermal tuner power. OR Thermal modulation efficiency. |
Heater resistance. |
Electrical bandwidth. |
Thermal bandwidth. |
Electrical Equivalent Circuit for INTERCONNECT model
The INTERCONNECT model can be used in the Cadence Virtuoso platform for PIC (photonic integrated circuits) and EIC (electronic integrated circuits) co-design and co-simulation. Electrical bandwidth of the ring modulator is defined by an electrical low pass filter (LPF) inside the INTERCONNECT optical model. When running a Spectre-INTERCONNECT co-simulation, the electrical bandwidth and loading effect of the ring modulator can be alternatively described by an electrical equivalent circuit, which is physically instantiated in Spectre, and in this case the LPF inside INTERCONNECT optical model must be turned off to avoid double counting the modulator’s electrical bandwidth.
This section describes the use of an electrical equivalent circuit for Spectre-INTERCONNECT co-simulation . The below figure shows the full schematic of the electrical equivalent circuit for a ring modulator, which includes an RC electrical load for the electrical phase shifter and a resistive load for the thermal phase shifter. The electrical equivalent circuit can be created by running CML Compiler with the “--interconnect_virtuoso” command line option. Depending on the model configuration, the RC electrical load and the resistive load can be conditionally instantiated.
Parameter |
Description |
Unit |
Comments |
Cj |
Junction capacitance |
F |
Bias dependent |
Rj |
Junction resistance |
ohm |
|
Cp |
Parasitic capacitance |
F |
|
Rp |
Contact resistance |
ohm |
|
R_thermal_tuner |
Heater resistance |
ohm |
Either a linear resistance value or non-linear resistance described by IV |
The figure below shows the use of the electrical equivalent circuit and the optical INTERCONNECT model for co-simulation case. The Cj voltage drives the optical INTERCONNECT model. In co-simulation, Spectre simulates the electrical equivalent circuit for its electrical bandwidth and loading effect, while INTERCONNECT simulates the optical INTERCONNECT model. In this case, the internal electrical LPF of the optical INTERCONNECT model must be turned off to avoid double counting the modulator’s electrical bandwidth.
Electrical Equivalent Circuit for Photonic Verilog-A model
The photonic Verilog-A model is compatible with Cadence Virtuoso design platform and its Spectre simulator. When simulating the photonic Verilog-A model for a ring modulator (RM) element using Spectre engine in Virtuoso, the electrical equivalent circuit and the photonic model are both implemented inside the compiled Verilog-A RM element as shown in the figure below. Spectre simulates both the electrical equivalent circuit for the RM’s electrical characteristics and the photonic RM model for its optical characteristics. The Verilog-A model for a RM element can be generated through CMLC by executing it with --veriloga_virtuoso command line option.