Harold Simulations

A HAROLD device simulation consists of solving the governing equations of the model at a set of bias currents, so as to obtain the characteristics of the device vs. current.

HAROLD has a number of simulation modes to choose from:

• Running mode
  • 1D: Solves self-consistently the various differential equations of the model in the vertical (y) direction only, assuming uniformity on the longitudinal (z) direction.
  • 2D (XY, option): as above but models variations of electrical and optical fields in both transverse directions.
  • 2D (YZ): Solves self-consistently same equations as in 1D mode but also considers longitudinal effects such as surface recombination and optical absorption at facets, and the non-uniformity of the optical field.
  • PICWave Model: a variation of the 1D isothermal model, this mode is used for producing material gain models which can be exported to PICWave.
• Execution mode
  • Isothermal: Simulates the device under “pulsed” operation i.e. ignores heating such that the temperature is fixed at a constant value throughout the whole structure.
  • Self-heating: Simulates the device under “CW” operation i.e. accounts for device heating model the heatflow within the device
  • Test: A quick diagnostic mode which simulates the device at zero bias - it allows you examine basic results so you check that your layer structure has been set up as intended.

Due to its detailed physical model, HAROLD can obtain a wide range of simulation results, including:

• 1D/2D Results (i.e. vertical/vertical-longitudinal profiles):
  • Electrostatic potential, electric field
  • Electron and hole Fermi energies
  • Conduction and valence band edges
  • Electron and hole densities (in bulk and QWs)
  • Electron and hole current densities
  • Recombination rates: SRH, Auger, spontaneous emission, stimulated
  • Heat flow and temperature profiles, profiles of different heat sources (Joule effect, non-radiative recombination, free-carrier absorption)

• Per-bias Results (i.e. vs. bias current/voltage/current density):
  • Optical powers for left and right-hand facets (optical output power, scattered and absorbed power)
  • Dissipated power due to Joule heating, non-radiative recombination, free carrier absorption
  • External slope efficiency for both facets (dP/dI)
  • Electron and hole densities (in bulk and QWs)
  • Active region temperature
  • Quantum efficiency
  • Lasing wavelength
  • Modal and material gain
  • Effective mode index change
  • Free carrier loss
  • Recombination rates (in bulk and QWs): SRH, Auger, spontaneous emission, stimulated

• Spectra:
  • Gain
  • Spontaneous emission
  • Refractive index

• Quantum well results:
  • Electron, light-hole, heavy-hole potentials
  • QQW wavefunctions and energy eigenvalues for electron, light-hole and heavy-hole sub-bands