Diode laser failure mechanisms can be divided into two main categories: infant mortality failures and wear out failures (see lifetime testing). Infant mortality failures can be caused by defects introduced during the manufacturing process of the diode lasers. These kind of defects can originate in semiconductor material during epitaxial growth for example.
Burn-in process is used to screen out infant mortality failures. In this process testing device is run for certain time (typically less than 100h) under controlled operating conditions. Typical operating parameters are tested before and after the burn-in. A notable change in parameters, when comparing before and after results, typically indicates high possibility for infant mortality failure.