Abstract
Variable attenuators for intense laser beams are very important in various laser applications. A new type of attenuator which exhibits a wide dynamic range and is insensitive to the polarization state of the beam is introduced. The attenuator is based on a rotatable zero-order halfwave plate, sandwiched between two identical bireflectance polarization prisms1,2 (LOLAs) (Fig. 1). The first prism splits the incoming beam angularly info s and p components. The separation angle δΦ is given by δΦ≈ na − n0, where n0 and ne are the ordinary and extraordinary refractive indices of the prism crystal, respectively. In the absence of a wave- plate, the second prism, oriented with its optic axis parallel to that of the first prism, cancels the angular splitting. Except for a small spatial separation δr, the two polarized beams reunite into an unpolarized one. For prism dimensions of ~1 cm, the separation δr is ~1-2% of the prism aperture. On insertion of the waveplate, each polarized beam splits again in the second prism. Thus four coplanar beams angularly separated by 2 × δΦ are generated. The attenuator output consists of the combined central two beams. It is parallel and essentially similar in its polarization state to the incoming beam irrespective of the waveplate orientation. The two side beams, which are polarized s and p, respectively, are damped.
© 1989 Optical Society of America
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