Your source of photonics CAD tools


A hetero-structure laser diode model

Harold VCSEL Laser Module



HAROLD/VCSEL is a full 3D model, computing the multiple optical cavity modes, electrical drift-diffusion, heat-flow and electron-photon interactions. Building on Photon Design’s 30 year experience in both EM and laser diode modelling, this provides a comprehensive integrated design environment for a variety of the VCSEL variations being explored by industry today, including QW materials, tunnel junctions, current blocking oxide apertures and more.

vcsel cross section

Modelling Scope

HAROLD/VCSEL covers the three main areas of modelling:



  • Built in full-vector 3D cavity mode solver for multiple modes

  • Scattering off oxide windows, contact apertures

  • Built-in far-field calculator

  • Built-in QW gain model, with databases for common materials InGaAsP, AlGaAs, InGaAlAs etc.


  • Self Consistent Poisson/drift-diffusion electrical model

  • Current confinement via oxide apertures or tunnel junctions 

  • Electrical Leakage


  • Full 3D thermal heat-flow model

  • Joule(I2R) heating, contact resistance heating

  • Recombination, FCA, IVBA heat sources

VCSEL Editor

Starting from your epitaxy recipe our updated user interface in Harold/VCSEL will make it easy to design your VCSEL, with features for easy definition of DBRs and positioning of contacts, tunnel junctions and oxide layers.

VCSEL editor

VCSEL device editor: a base layer structure is modified via the use of etch and grow processes to allow careful placement of current-blocking oxide apertures (displayed in the red box) and ring-contacts.

Simulation Results

Harold/VCSEL is capable of generating a wide variety of simulation results, giving a detailed insight in device behaviour. These include:

- Temperature, heat sources

- Current and carrier density

- Optical mode/far-field

Detailed Cross-Sectional and Plan Profiles

optical mode and temp distribution

Profile of optical mode (left) and temperature (right) inside the cavity

far field intensity of VCSEL output

Far-field intensity profile of VCSEL output

current density distribution

Current density profile showing cross-section (left) and plan (right) views of current flow through a tunnel junction

Steady State Device Results

- LIV Curves

- Temperature and dissipated heat source powers

- Recombination currents

- QW gain, carrier density, FCA/IVBA

VCSEL LI curves

VCSEL LI curves at different ambient temperatures

Time-Domain Results Spectra

- Time evolution of optical power and carrier density

- Laser output optical spectra (power spectral density), RIN spectra

- Lasing linewidth

radial carrier density profile

Time-evolving radial carrier density profile for laser switch-on


laser output spectrum

Laser output optical spectrum

Compound Semiconductor Article
Please see this article which is published in Compound Semiconductor in June 2020 for more information about the Harold VCSEL Module PDF
Coming Soon!

As the development of Harold/VCSEL continues, we look forward to adding further features and functionality in subsequent releases, including:

- Side current injection

- Support for wafer bonding

- Time-domain dynamics/modulation response spectra

- And more...

Please contact us if you are interested in these or have any further feature requests.