The ring_modulator_parameterized photonic model is specifically tailored to modelling parameterized ring modulators or ring filters. It provides a method of creating both single-bus and double-bus elements, which accurately model electrical and thermal modulation. The model supports radius, coupling length, coupling gap (through and drop), junction_fill_factor , high_loss_waveguide_fill_factor, and thermal_fill_factor as parameters. This model also supports fine-tuning of model properties to match user provided figures of merit. Note that the tuning capability only works when the fill factors are set to their default values. The ring_modulator_parameterized photonic model currently does not support statistical modeling.
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.
Lumfoundry Templates: Ring Modulator Parameterized
Quality Assurance Test: ring_modulator_parameterized QA
Statistical Modeling Support: No
Supported Parameters: radius, coupling_length (Lc), coupling_gap (through and drop), junction_fill_factor , high_loss_waveguide_fill_factor, and thermal_fill_factor.
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.
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 exist Disable: th_neg and th_pos ports do not exist |
Single/double bus |
Single Bus: opt_3 and opt_4 ports do not exist Double Bus: opt_3_ and opt_4 ports exist |
Model Information
- This model assumes that the waveguide mode data does not change with radius.
- This model assumes thermal bandwidth to be constant over all bias range.
- This model only supports single mode operation.
- This model does not support statistical modeling.
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 parameterized 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 per unit length |
F/m |
|
Rj |
Series resistivity |
Ω*m |
|
Cp |
Parasitic capacitance |
F |
Capacitance between metal contacts. |
Rp |
Contact resistance |
Ω |
Resistance of metal contacts. |
R_thermal_tuner |
Heater resistance |
Ω |
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. In co-simulation, Spectre simulates the electrical equivalent circuit for its electrical bandwidth and loading effect, while INTERCONNECT simulates the optical INTERCONNECT model. The Cj voltage drives 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 parameterized 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 parameterized RM’s electrical characteristics and the photonic parameterized RM model for its optical characteristics. The Verilog-A model for a parameterized RM element can be generated through CMLC by executing it with --veriloga_virtuoso command line option.