Detection for production laser damage testing at 1.06μm may be accomplished by a single scheme of flash detection. This scheme uses the test wavelength, 1.06/OT, to detect catastrophic damage events and is sufficient to detect the plasma associated with catastrophic damage, the failure morphology typical of production damage testing.
The detection scheme consists of a fiber optic bundle used as a light pipe and a photomultiplier tube as a detector. Uhen introduced into the target area, the collection end of the light pipe is the only element of the detector that need be in proximity to the target area. Since the light pipe has a wide acceptance angle, precise location and orientation of the light pipe end is not required. Therefore, the detector may be moved in and out easily without compromising detector performance. The detector is used in conjunction with electronics that allow the user to define a non-damage level of scatter. When damage occurs and the characteristic plasma plume is formed, a comparator detects the signal exceeding the set threshold and registers a damage event.
The simplicity and low cost aspects of the detection scheme make it a good candidate for all production damage testers at l.06μm. Furthermore, the detection apparatus may be linked electronically to the test laser to shut off the test source upon detection of damage to prevent gratuitous damage to the sample under test. The incorporation of such a binary damage detector is suitable for use in an automated and, therefore, enclosed (Class I) damage tester for use on factory floors.