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A hetero-structure laser diode model

Harold VCSEL Laser Module



HAROLD/VCSEL is a full 3D model, computing the mutliple 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, current blocking 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

  • 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 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 and plan views of current flow through oxide layer aperture

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

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

- Tunnel junctions

- Time-domain dynamics/modulation response spectra

- And more...

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