Diode lasers are very reliable under normal operating conditions. However, like most semiconductor devices, they can be damaged or destroyed by inadvertent electrical or static discharges (ESD). This optical damage can happen even with a momentary over-current. Here, absorption and temperature build up in a positive feedback loop that eventually leads to material destruction. Symptoms of damage include reduced output power, threshold-current shift. 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. Protecting a laser diode boils down to one core principle: rigorously controlling the electrical current and thermal environment at all times.
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