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Thermal switch 2x2 (Statistical) - Lumfoundry Template

A statistically enabled unbalanced 2x2 thermo-optic switch model. For this model figure of merits such as FSR, IL and thermal Ppi are considered as statistical parameters. In a FOM based statistical model, there is no need to find the statistical data for physical root cause of the variation and FOM measurements can be directly used as statistical data.

For information on statistical CMLs, see Statistical CMLs .

Note: For legacy data format (2022 R2.4 and older) please visit following link:

Thermal switch 2x2 (Statistical) - Lumfoundry Template (Legacy)

Template: thermal_switch_2x2_stat_te_c

Photonic Model: mach_zehnder_modulator_2x2

Quality Assurance Test: mach_zehnder_modulator QA

Statistically Enabled Parameters:

Balanced: Ppi_thermal

Unbalanced: Ppi_thermal, resonant_wavelength, FSR, ER, IL

Parameters: imbalance length, switch length.

Interoperability with Cadence Virtuoso:

  • Circuit design flows using INTERCONNECT model: Yes.
  • Circuit design flow using photonic Verilog-A model: No.

Modeling Data

The source data template for a statistically enabled unbalanced 2x2 thermo-optic switch element can be divided into two sections.

  1. For new users (continue with the following section: Basic data requirement)
  2. Advanced users ( continue with section: Complete Data Requirement )

The statistically enabled unbalanced 2x2 thermo-optic switch template can be used to create an advanced compact model for a custom statistically enabled unbalanced 2x2 thermo-optic switch. The template contains a lot of different modeling data to create an accurate model. However, not all these data need to be updated by users. The fastest and simplest way to modify the template data and create a custom compact model is to only update the data listed in the 'basic data requirement section' below, while all the remaining data (which are illustrated in detail in subsequent sections) can stay at their default value.

Note: Advanced users please jump start with Complete Data Requirement (for advanced users) section.

Basic data requirement (for new users)

The basic and minimum data required to build the statistically enabled unbalanced 2x2 thermo-optic switch model is described below.

general

"general" is a struct with following fields:

Field Type Description
description string A string containing a brief description of the model, which will be displayed to the end user.
notes cell

A cell array providing model notes which will be displayed to the end user. Each element of the cell is a struct with the fields:

  • property: String with the name of the note.
  • value: String with the contents of the note.

ports

"ports" is a struct with following fields:

Field Type Description

opt_1

 struct with fields described in table below Port definition corresponding to the first and second input optical ports

opt_2

opt_3

 Port definition corresponding to the first and second output optical ports

opt_4

th_neg_top

Port definition corresponding to the contacts of the "top-arm" thermal tuner

th_pos_top

th_neg_bot

 Port definition corresponding to the contacts of the "bottom-arm" thermal tuner

th_pos_bot

Each struct above consists of following fields:

Field Type Description
name string The name of the port, which will be visible to the end user. This name should be consistent with the name that will be used for netlisting.
pos string

The side of the model which the port will be displayed on, either "Left", "Right", "Top", or "Bottom"
order number

The order in which the port is listed in a netlist.

parameters

"parameters" is a struct with following fields:

Field Type Description
wg_length
 struct with the fields described in the table below

The length of the thermal phase shifter.
imbalance_length

The imbalance length of the MZI.

Note: This parameter should be set to 0 for a balanced MZI.

Each struct above consists of following fields:

Field Type Description

name

string

The name for display in the Property View window. 

default

number

The nominal value of the parameter in SI unit.

visible_to_user

 boolean

A flag to enable/disable the parameter visibility.
min

number

Minimum allowed value if the visible_to_user is set to True.
max

number

Maximum allowed value if the visible_to_user is set to True.

model_data

"model_data" is a struct with following fields:

Field Type Description

longer_arm

 number

Denotes which arm is longer for imbalanced modulators. Options are:

  • upper arm = -1
  • lower arm = 1

Note: This parameter is not required for a balanced MZM.

mode_data

cell

1 x 1 cell array. Each element of the cell is a struct with fields:

  • name: string with the name of the mode ("TE" or "TM")
  • ID: integer to identify the mode, which should be 1 for "TE" and 2 for "TM". These should be consistent across the entire CML.

This model only supports a single mode.

waveguide_data

struct with fields described in waveguide_data table

Data required for modeling the waveguide sections.
thermal_tuner_data

struct with fields described in thermal_tuner_data table

Data required for modeling the thermal tuner.
th_eq_ckt_data

struct

Thermal equivalent circuit described by either Current (Amp) versus bias voltage (V) characteristic of the heater for the default phase shifter length with required field of:

  • voltage: Bias voltage data points as matrix.
  • current: Current data points as a matrix.

The IV data are linearly interpolated to obtain the electrical behavior. 

or resistance (\(\Omega)\) of the heater for the default length of the phase shifter with required field of:

  • R_thermal_tuner: Heater resistance as a single number.
 
Note:
  • Using a linear model is suitable for resistive heaters, but for voltage-dependent models an IV characteristic should be used instead.
  • If IV data is provided, it will take preference over R_thermal_tuner data 
  • If I-V data is provided:
    • At least two bias points must be provided. 
    • Bias voltage and current values must be positive. 
    • These data will be used instead of a resistance value, if provided. 
    • The I*V values must fall within the range of power values provided in thermal_tuner_data. 

thermal_tuner_data

Note: For a Mach-Zehnder without thermal tuner, this struct should not be provided.

Field Type Description

bandwidth_data

 struct

A single value containing the 3-dB cutoff frequency of the thermal phase shifter.

waveguide_data 

Note: The fields are only required for waveguide sections with non-zero length. See Internal Model Diagram in photonic model page for a diagram showing the role of each section. 

Field Type Description

wavelength

number

Center wavelength (m) of the band for which the mode properties are provided.

temperature

 number

Temperature (K) for which the mode properties below are provided.
waveguide_hangover_left

struct with fields described in table below

 

 

Mode properties for modeling the right and left hangover waveguide sections
waveguide_hangover_right
waveguide_passive_right

Mode properties for modeling the right and left passive waveguide sections
waveguide_passive_left
waveguide_thermal_tuner

Mode properties for modeling the thermal phase shifter waveguide section at 0 V bias

Structs listing mode properties for different waveguide sections consist of following fields:

Field Type Description

length

number

Length (m) of the waveguide section. 

Note: This field is not required if the length is set as a parameter or otherwise described by other variables such as radius.

neff

 number

Unperturbed effective index of the waveguide section (no electrical or thermal tuning applied).
ng

number

Group index of the waveguide section.
dneff_dT

number

Effective index temperature sensitivity (1/K) of the waveguide section.
loss

number

loss (dB/m) of the waveguide section.

FOMs

"FOMs" is a struct with fields below. This data is required for CML Compiler to run quality-assurance tests on the final model. It is also optionally used by CML Compiler to fine-tune the internal model to provide the expected behavior.

If the source physical data provided for the model is not consistent with the figures of merit (FOMs) provided (meaning the actual FOM values resulting from physical parameters differ from provided FOM data), the model can tune the provided physical data to match the FOMs to the provided values. For more information, see Tuning Active Compact Models.

Field Type Description

IL

struct with the fields described in the table below

The overall insertion loss (dB) of the MZM in the off-resonance region as explained in the Spectrum Data Visualization in photonic model page.

Note:  This FOM will be enabled internally to enable statistical variations if IL is a statistical parameter.

FSR

 struct with the fields described in the table below

The free spectral range (m) of the MZM provided as a struct.

Note:

  • This FOM will be enabled internally to enable statistical variations if FSR is a statistical parameter.
  • This parameter is not applicable for a balanced MZM.
notch_wavelength struct with the fields described in the table below

The resonant wavelength (m) of the MZM at a temperature of 300K with no applied electrical or thermal phase shift.

Note:

  • This FOM will be enabled internally to enable statistical variations if notch_wavelength is a statistical parameter.
  • This parameter is not applicable for a balanced MZM.
Ppi_thermal

struct with the fields described in the table below

Power (W) for pi phase shift of the thermal tuner (single arm) for input power range described by "ref1" and "ref2" in the struct.

Note: This FOM will be enabled internally to enable statistical variations if Ppi_thermal is a statistical parameter.
ER  

struct with the fields described in the table below

The extinction ratio (dB) of the model (as explained in the Spectrum Data Visualization in photonic model page).

Note:

  • This parameter is not applicable for a balanced model.

S13

struct with fields described in table below

 

Transmission (dB) from optical port 1 (1st input) to optical port 3 (1st output) at zero bias.

Note:

  • Tuning for this FOM is not enabled. 
  • This parameter is only applicable for a balanced MZM.

S14

Transmission (dB) from optical port 1 (1st input) to optical port 4 (2nd output) at zero bias.

Note: This parameter is only applicable for a balanced MZM.

Each struct above consists of following fields:

Field Type Description

value

number

The nominal value for the FOM in SI unit.

tuning

boolean

A flag to enable or disable FOM tuning.
ref1 (if applicable)

number

 Point(s) at which the nominal FOM were measured. This parameter can be voltage or power data points depending on the FOM definition.
ref2 (if applicable)
 

number

QA

"QA" is a struct with following fields:

Field Type Description

parameters

struct with fields described in parameters table

Parameter values used for setting up the QA test bench.

parameters

Field Type Description
wavelength number

The center wavelength for QA tests.
thermal_BW_bias
 number

The bias voltage (positive) of the thermal switch for thermal bandwidth test. 

Note: This should only provided for a model with thermal tuner. 

 

Complete data requirement (for advanced users)

The complete data section provide a complete reference of data supported by the statistically enabled unbalanced 2x2 thermo-optic switch model including the basic required data described in the previous section. The descriptions of all the fields in the statistically enabled unbalanced 2x2 thermo-optic switch source data template are described below.

general

"general" is a struct with following fields:

[[snippet||11549514081811]]

ports

"ports" is a struct with following fields:

[[snippet||11936678879891]]

Each struct above consists of following fields:

[[snippet||11549759363603]]

parameters

"parameters" is a struct with following fields:

[[snippet||11881543031187]]

Each struct above consists of following fields:

[[snippet||11720299494931]]

model_data

"model_data" is a struct with following fields:

[[snippet||11936801037075]]

Structs listing mode properties for different waveguide sections consist of following fields:

[[snippet||11653970537235]]

FOMs

"FOMs" is a struct with fields below. This data is required for CML Compiler to run quality-assurance tests on the final model. It is also optionally used by CML Compiler to fine-tune the internal model to provide the expected behavior.

If the source physical data provided for the model is not consistent with the figures of merit (FOMs) provided (meaning the actual FOM values resulting from physical parameters differ from provided FOM data), the model can tune the provided physical data to match the FOMs to the provided values. For more information, see Tuning Active Compact Models.

[[snippet||11905242526483]]

S13

struct with fields described in table below

 

Transmission (dB) from optical port 1 (1st input) to optical port 3 (1st output) at zero bias.

Note:

  • Tuning for this FOM is not enabled. 
  • This parameter is only applicable for a balanced MZM.

S14

Transmission (dB) from optical port 1 (1st input) to optical port 4 (2nd output) at zero bias.

Note: This parameter is only applicable for a balanced MZM.

Each struct above consists of following fields:

[[snippet||11653867902995]]

QA

"QA" is a struct with following fields:

[[snippet||11937399425555]]

statistical 

"statistical" is a struct with fields below. This struct is optional and is only required for statistical compact models.

Note: To allow CML Compiler to build statistically enabled models, the statistical_parameter_status has to be defined in the XML file. For more information, see Statistical CMLs.

Field Type Description
parameters

struct

Each field of this struct defines one statistical parameter for the model. These fields should have names following "parameter_X" where X is an integer and follow the structure described in statistical parameters table.

Note: This data is required for CML Compiler to enable statistical modeling.
QA

struct with fields described in QA table

Defining QA settings for statistical QA.

statistical parameters

[[snippet||11647965606547]]

slope_neff

number

The sensitivity of the effective index of the active waveguide with respect to the X-th statistical parameter defined as d_neff / d_parameter_X.

Note: Only provide this field if the statistical parameter affects the effective index (see thermal_switch_2x2_stat_te_c).
slope_ng

number

The sensitivity of the group index of the active waveguide with respect to the X-th statistical parameter defined as d_ng / d_parameter_X.

Note: Only provide this field if the statistical parameter affects the group index (see thermal_switch_2x2_stat_te_c).
slope_notch 

number

The sensitivity of the notch (resonant) wavelength (m) of the mach-zehnder modulator with respect to the X-th statistical parameter defined as d_notch / d_parameter_X.

Note: Only provide this field if the statistical parameter affects the notch wavelength (see thermal_switch_2x2_stat_te_c).
slope_IL

number

The sensitivity of the insertion loss (dB) of the mach-zehnder modulator with respect to the X-th statistical parameter defined as d_IL / d_parameter_X.

Note:

  • Only provide this field if the statistical parameter affects the insertion loss (see thermal_switch_2x2_stat_te_c).
  • This is only available for unbalanced models.
slope_FSR

number

The sensitivity of the free spectral range (m) of the mach-zehnder modulator with respect to the X-th statistical parameter defined as d_FSR / d_parameter_X.

Note:

  • Only provide this field if the statistical parameter affects the free spectral range (see thermal_switch_2x2_stat_te_c).
  • This is only available for unbalanced models.
slope_ER

number

The sensitivity of the extinction ratio (dB) of the mach-zehnder modulator with respect to the X-th statistical parameter defined as d_ER / d_parameter_X.

Note:

  • Only provide this field if the statistical parameter affects the free spectral range (see thermal_switch_2x2_stat_te_c).
  • This is only available for unbalanced models.

statistical QA

[[snippet||11914319040403]]

Associated files

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