In a beam sampler, percentage of reflected light is determined by the Fresnel reflection from a single surface. At the nominal 45° AOI the beam sampler reflects approximately 10% and 1% for s- and p- polarizations, respectively. For measuring beam power, the beam sampler should be oriented such that the laser is p-polarized. This choice will maximize transmitted power and attenuate power incident on the detector. Depending on the polarization of the incident beam, front surface reflectance from 1-10% can be attained at 45° incidence.

Optics with perfectly parallel faces are unsuited for use as reference elements in laser setups as reflections from both surfaces would be collinear resulting in undesired large period fringes. The introduction of a slight wedge causes unwanted reflections from the second surface to be deflected from the optical path. The back surface (S2) of this beam sampler is slightly wedged. The laser beam should enter the non-wedged surface (S1) where an arrow on the side points to.