Hierarchy of laser models in Lumerical INTERCONNECT

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:

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:

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:

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, Fabry-Perot, DFB, external ring mirrors, etc.
• External feedback effects
• Self-heating 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: