A Simple and Reliable Dye Laser System for Spectroscopic Investigations

For most experimental applications where organic dye lasers are used as light sources, it is necessary to narrow the spectral output which is up to a few hundred Ängstroms wide. Spectral narrowing down to 0.5 — 1 Ä can be achieved by using a diffraction grating as one of the resonator mirrors a set of prisms2 or an interference filter inside the laser cavity3. Further reduction of the emission bandwidth is possible if an additional dispersive element is introduced into the cavity. B R A D L E Y et al. 4 obtained a spectral width of the dye laser emission of about 0.01 Ä by using a Fabry-Perot interferometer. The same value is reported by W A L T H E R and H A L L 5 , who inserted a two stage polarisation interference filter, similar to the device described by L Y O T 6, into the cavity. The spectral resolution of all known dispersion elements is limited by the divergence of the incident light beams. For flashlamp pumped dye lasers, divergences up to a few mrad are possible because the pumplight can produce optical inhomogeneities in the dye solution. Since interference filters have a very small beam divergence sensitivity, they are superior to all other configurations for spectral narrowing 7' 8. In this paper we want to describe a very simple and reliable dye laser setup which is able to produce laser emission with a bandwidth of less than 0.005 Ä. This small spectral width could be reached by using only a two stage wavelength selector consisting of an interference filter and a Fabry-Perot interferometer inside the laser cavity.