Blue-violet nitride laser diode operate ot relatively high current density of the range of 5-10 kA/cm2. The degradation of these diodes occurs predominantly by the increase of their threshold current. There are two the most important factors influencing the degradation speed:

2.Operation and junction temperature (very fast, exponential dependence)

3.The degradation rate can be calculated form the following equation:

Where:

A – constant

I – operating current

EA – activation energy of      degradation (typically 0,35 to 0.4 eV)

k – Boltzman constant

THS – temperature of the   heat sink

RT –  thermal resistance  (for TO56 package, THS=25-30 K/W)

U – operating voltage

Temperature of the active region can be calculated from the following equation:

Typical dependence of degradation rate on temperature for a fixed currents.