A severe over-current or over-voltage power surge can cause localized heating and other harmful phenomena, which, under extreme conditions, can actually fracture the laser diode die (we have seen this under a microscope, brought on by high levels of ESD). One of the damage mechanisms is optically related, and occurs when the laser diode is producing light (referred to as “lasing”), and the optical energy density exceeds the laser diode's integral mirrors' reflective capacity. When this occurs, the mirrored surface permanently loses its reflectivity. It has burned thru 90% of this particular closed loop. It keeps burning but not getting thru the last 5 -10 %. Appreciate the support I've received on this forum. Placing devices in parallel adds a bit more complexity to the testing due to the variations in the devices. Being the facet the weakest link for power surges, it is important to improve its. Take these steps to protect your laser diodes from electrostatic discharge, excessive current levels, current spikes, and transients. This optical damage can happen even with a momentary over-current.
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