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Вот, например --> https://assets.newport.com/webDocuments-EN/images/AN33_Laser_Diode_Activation_IX.pdf

Almost all commercially available laser diodes have been screened to remove devices that are likely to suffer from infant mortality. For many types of lasers, the remaining good devices exhibit a wearout failure mode which is characterized by a slow degradation of light output over time when the laser is operated at a constant temperature and forward current. If the laser is operated in a feedback loop that maintains a constant light output, wearout failure is characterized by a steady increase in the required forward current. In this case, time to failure is usually defined as the time at which the forward current has increased by 20% to 50% of its initial value.