INTERCONNECT has three laser models and each has different features and is suitable for different applications. The models ordered from simpler to more complex are: CW Laser model (simple source model), DM Laser model (0D rate equation model) and TW Laser model (1D travelling wave model). Moving from simpler models to more complex ones there are more physics effects included and the computational cost is higher. Following is an illustration of the laser models features:
The following table shows the comparison of the three models:
Primitives  Physical Model  Required Data  Input Electrical Signal  Optical Ports  Selfheating  External Cavity Feedback Support 

CWL  No  Basic (FOM) 
No (but electrical input can be added within a compound element) 
One unidirectional output 
No  No 
DML  Yes, 0D  Medium 
Yes (direct modulation bandwidth) 
One unidirectional output 
No  No 
TWLM  Yes, 1D  Complex 
Yes (direct modulation bandwidth) 
Two bidirectional outputs 
Yes  Yes 
CWL (Continuous Wave Laser)
The CWL model has one unidirectional optical output port and doesn't have electrical input port.
Some features of this model are:
 Instantaneous turn on
 Relative intensity noise (RIN) is input parameter and it is constant in frequency (added as random white noise in time domain)
 Linewidth is input parameter
 Simplified time domain optical output is given by \(x=\sqrt{P} e^{i \phi(t)}\), where
 \(P\) is the desired power (input option), and
 \(\phi(t)\) is a random phase calculated from input linewidth
 Simplified multimode CWL type exists
Though this model doesn't have electrical input, electrical input can be added in a custom compound element based on input LIV table:
The LIV curve of the above model is shown below:
Input requirements  Figure of merit (FOM)  

Linewidth  RIN  Peak Frequency  IV  LI  LIV 
DML (Directly Modulated Laser)
The DML model is based on the 0D rate equation. Some features of this model are:
 Dynamic modulation with an electrical signal
 Unidirectional optical output
 Spontaneous emission model
 RIN and linewidth are results of calculation, rather than input
This model can be used for generating a laser compact model for a PDK when combined with measurement data. An example of this is the collaboration with Analog Photonics on a DFB laser compact model (more details in our blog post and white paper). The data requirement for the compact model is:
Input requirements  FOM  

Frequency 
Gain Coefficient 
Photon Lifetime 
Electron Lifetime 
Fraction of Spontaneous emission coupled to lasing mode 
Nonlinear gain saturation factor 
Carrier number at transparency 
Differential Quantum Efficiency 
Linewidth enhancement factor

LI  RIN 
Validation of this laser compact model against device measurements is shown below:
TWLM (Traveling Wave Laser Model)
The TWLM model is based on the 1D traveling wave rate equations. Some features of this model are:
 Gain and spontaneous emission as a function of frequency, carrier density, and temperature can be imported from physical simulation or measurement
 Dynamic modulation with an electrical signal
 Two bidirectional optical ports
 RIN and linewidth are results of calculation, rather than input
 Simulation of SOA, FabryPerot, DFB, external ring mirrors, etc.
 External feedback effects
 Selfheating effects
 Multisection laser structures definition. For detailed instrutions, refer to: Laser TW (TWLM)  INTERCONNECT Element – Ansys Optics
Combining repeatable measurements with simulation and fitting, parameters for the TWLM compact model can be extracted to build a Semiconductor Optical Amplifier (SOA) compact model. This application is a collaboration with Fraunhofer HHI. For more details, please visit this blog and case study.
Following is the TWLM model required input and measurement results:
Input Requirements (fitting may be feasible for some missing data) 
FOM  

Active layer length 
Active layer width 
Active layer thickness (cumulative thickness of QWs) 
SCH layer thickness (if SCH enabled) 
Carrier capture/escape rates (if SCH enabled) 
Carrier recombination rate vs. carrier density (coefficients or table) 
ASE 
Power gain 
Modal gain vs. carrier density and wavelength (Lorentzian or user defined) 
Waveguide loss 
Effective index 
Group index 
Current injection efficiency 
Mode confinement factor (if material gain used instead of modal gain) 
LI  RIN 
Notes:
