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Harold

A hetero-structure laser diode model

XY Laser Module

Harold’s XY Laser Module extends Harold’s algorithm so that the lateral structure of laser devices is accounted for. It uses the same physical model as a Harold 1d simulation but solves the electrical/optical/thermal problem on a 2D (XY) grid, the starting point being a 2D cross-section, rather than a single 1D epilayer stack. In addition, it supports insulating layers and graded etching and allows n and p-contacts can be on the top of the structure. All this makes it ideal for the detailed modelling of simple ridge waveguide and SOI hybrid laser structures alike.

The XY Laser Module uses the Harold’s existing layers editor, trap definition editor and mesh policy editor, making it easy to adapt and use existing Harold projects to set up XY simulations. The XY Laser Module also has the same execution modes as a Harold 1D simulation: Test mode (for quick diagnostics), Isothermal (pulsed), and Self-Heating (CW) modes.

Cross-section editor

The XY Laser Module’s cross-section editor allows you to fully define a laser’s 2D cross-section. A cross-section is composed of a number of vertical slices, of varying widths, each of which uses its own (or a shared) epitaxial layer structure. Slices can be etched to varying depths and can also have graded etching. Each slice can have its top or bottom connected to the bias contact, the ground contact, or no contact at all.

Cross section editor

XY Cross-section Editor: A ridge waveguide structure with graded etching: in this case, all slices share a common layer structure; the bias contact is attached to top of ridge, ground contact extends across the bottom of all slices

Simulations results

In addition to Per Bias results (i.e. vs. bias current/voltage/current density), Harold XY produces 2D lateral-vertical profiles of various quantities, including: 

  • Electrostatic potential and electric field (vector plot)

  • Electron and hole Fermi energies

  • Conduction and valence band edges

  • Electron and hole densities (in bulk and QWs)

  • Electron and hole current densities (vector field plots)

  • Recombination rates: SRH, Auger, spontaneous emission, stimulated

  • Temperature

  • Optical mode

Conduction band

XY profile of the conduction band within a ridge waveguide laser

Temperature profile

XY profile of temperature in a ridge waveguide laser – showing how temperature increases laterally,
away from the ridge which lies under the heatsink

Auger profile

XY profile of Auger recombination in QW of ridge waveguide laser – showing reduced Auger rate
in centre of waveguide where mode intensity, and therefore stimulated recombination, is large

Comparison with PICWave, Harold and Harold EAM

Please see here for a comparison of the active component (laser diode, SOA, modulators etc.) modelling capabilities of PICWave, Harold, Harold XY and Harold EAM.