Traditional laser hair caps use a type of laser called through-hole lasers—or To-Can lasers. Traditional To-Can laser caps must be manufactured by hand, exposing the lasers to an electrostatic discharge during production. Electrostatic discharge—also known as ESD—is the single leading cause of premature laser-diode failure.
Through-hole lasers do not have glass to cover the laser window. This causes the laser to accumulate debris during production, which can cause malfunction of the laser and affect the beam and power output. Also, the through-hole laser soldering process can overheat the laser.
This damage that occurs in the manufacturing process of traditional laser caps may weaken the device—yet does not usually show any outward signs of this. The resulting degradation in performance may appear long after the initial damage takes place. When this finally occurs, it might be falsely attributed to other causes and/or ignored by the user. Damage may not be apparent and may surface as a latent failure.
Results may include reduced power output, a shift in the threshold current, change in divergence, difficulty focusing, and ultimately, failure to lase.