Image Number 3 for United States Patent #4489477.
A method for screening double heterostructure laser diodes before mounting and packaging is disclosed. At a normal laser diode operating temperature, a range of pulsed current is passed through the laser diode and the lasing threshold current and slope efficiency of the laser diode are monitored. The laser diode is then subjected to a burn-in process in which it is driven at a high junction temperature for an extended time period. Subsequently the lasing threshold current and slope efficiency are again monitored by applying the same range of pulsed current at the normal operating temperature. If either the threshold current or the slope efficiency have changed by more than a predetermined amount, the laser diode is rejected. Otherwise, the laser diode is gauged as likely to have a lifetime greater than a predetermined value at normal operating conditions so warranting further testing prior to installation into a laser package.