Lasers.

摘要

A laser includes mirrors 2, 3 and 4 which together define a laser cavity. The intermediate mirror 3 is inclined with respect to the vertical when the laser is operated in an orientation with the mirror 2 uppermost as illustrated. This ensures that any debris which would otherwise contaminate the mirror 3 and reduce its optical efficiency is deflected away from the laser cavity by the reflecting surface into the container 8. This process is aided by vibration means 10 and a heating coil 9 which ensures that molten material landing on the mirror does not solidify. In an alternative embodiment (not shown) the lowermost mirror is protected by a transparent member which acts as a deflecting surface.