Our 3 mm thick Ultrafast Laser Beam Sampler is designed to minimize pulse dispersion while splitting off, or sampling, a beam by Fresnel Reflection for beam monitoring applications. The N-BK7 substrate is uncoated on the front surface to achieve beam division by Fresnel Reflection. The back surface is antireflection coated to prevent ghosting. A slight wedge in the substrate virtually eliminates internal fringes.
In a beam sampler, percentage of reflected light is determined by the Fresnel reflection from a single surface. At the nominal 45° AIO 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.
N-BK7 is an excellent lens material for most visible and near infrared applications. It is the most common borosilicate crown optical glass, and it provides great performance at a good value. Its high homogeneity, low bubble and inclusion content, and straightforward manufacturability make it a good choice for transmissive optics.