HAROLD- A hetero-structure laser diode module

This module adds detailed heterostructure modelling to CLADISS-2d. In 1D mode, HAROLD solves the appropriate differential equations in the vertical direction, for a quantum well laser with arbitrary vertical  multiplstructure and composition. Both single ande quantum well lasers can be modelled. A state of the art capture/escape model for carriers in a quantum wells is implemented. Both pulsed (isothermal) and CW (self-heating) operation conditions can be simulated. Materials include ternary and quaternary alloys. In 2D mode, Harold will model longitudinal effects as well for simple Fabry-Perot cavities.

• Electrical model - self consitent solution of Poisson Equation, drift-diffusion, and capture/escape for both holes and electrons. 

• Thermal model Full vertical-longitudinal solution of the heat flow equation, including the substrate, the metal contacts and the heat sinks. Power dissipation is treated locally and includes Joule, non-radiative recombination, free carrier absorption, excess power distribution, mirror scattering and mirror absorption. 

• Optical model Photon distributed according to the optical mode of the laser cavity. The total photon density is determined considering the gain/loss balance in the full cavity. 

• Capture/escape In QW regions, thermal equilibrium between confined and unconfined carriers is not assumed, but described by means of appropriate capture/escape balance equations. 

• Quaternary alloys Utilization of quaternary allows is fully supported through the material database. 

• Gain model Material gain for quantum well lasers is computed as a function of the wavelength and carrier concentration, using a parabolic band approximation. 

• Recombination Shockley-Read-Hall, Auger, stimulated and spontaneous recombination processes are included. Advanced features, such as arbitrary specification of deep trap levels, are allowed on a layer-per-layer basis. 

• Surface recombination Recombination at the facets is included via deep trap levels at the mirror. 

• Bandgap narrowing Carrier-induced bandgap narrowing is included. 

• Quantum well The program wil determine the energy levels by solving Schrodinger’s equation; this data is then used in the gain computa-tions. 

• Strain The effect of strain on the QW levels is included. 

• Thermal overhang Heat-sink overhang is implemented. 

• Non-injecting mirror Suppression of current injection at the mirrors is implemented. 

• Absorbing mirror Photon absorption attenuation at the mirrors is implemented

The adjacent figure is a 2D Harold simulation showing the temperature rise towards the facet of a high power laser.

The adjacent figure is an analysis of the main heating mechanisms in a high power pump laser:

• P-exc : excess power - spontaneously emitted photons and scattered stimulated emission.
• P-nr : non-radiative recombination
• P-joule : joule heating
• P-fc : free-carrier absorbtion

General
What is CLADISS-2D?
-Calculation Method 
-Structure description
-Waveguide model
-Grating model
-Electrical model
-Graphical tool

Time domain response
Features List
Generic structures
Platforms
Customer support
Harold
Features
Facet heating
Heating mechanisms