Photochemistry and Spectroscopy Department

Institute of Physical Chemistry, Polish Academy of Sciences


For some spectroscopic applications (Raman spectroscopy, single molecule detection) there is a need to use separate Ar or Kr laser lines free from any contamination of broadband plasma radiation. Instead of buying a set of narrow-band interference filters we propose to use a compact device. It consists of two flint prisms. Radiation from the laser passes 16 times through the prisms (see Figure). Polarised “monochromatic” laser lines enter the prisms under ca. Brewster angle and are totally reflected onto the prisms. Therefore, losses of polarised laser radiation are not significant. When using a diaphragm placed at some distance from the separator, only a monochromatic line filtered out from plasma background passes through the diaphragm hole.

Separator operation:
The operation is shown in the Figure, where A – is the side view, and  B is– the top view of the optical system. The arrows indicate the direction of laser light propagation in the prisms. Simultaneous rotation of both prisms around points 0 in the direction marked by gamma allows selection of a specific laser line passing through the diaphragm.