Abstract: An attenuator for high power laser beams, the attenuator has an annular b dump through which the beam passes diametrically and in which the beam passes successively through a pair of pivoting transmissive and reflective element. These elements are individually mounted on intermeshed gears so that the elements are adjustable through equal and opposite angles. At each element a portion of the beam is reflected toward the dump and a portion transmitted, the relative energy in each portion being determined by the angle of the elements to the beam so that adjustment of this angle determines the amount of attenuation. The beam is offset oppositely by refraction at each element so that the attenuator does not change the beam path. The elements are, preferably, elements commonly used as edge filters, that is, interference filters having an abrupt monotonic transition with wavelength from reflection to transmission.

Abstract: An apparatus and method for measuring optical coupling coefficients is disclosed using the thermal expansion of a sample to reduce an externally applied tensile load of predetermined magnitude. The sample is illuminated with a known amount of incident energy. The absorption of this energy expands the sample which reduces the tension in the sample. The measurement of the tension reduction permits a direct calculation of the coupling coefficient .alpha., through use of the known parameters of a sample.