Quasiunimodal tunable pulsed dye laser at 440 nm: theoretical development for using a quad prism beam expander and one or two gratings in a pulsed dye laser oscillator cavity.

In the first section of this paper a theoretical discussion is presented for the performance of a pulsed dye laser oscillator cavity, without an intracavity etalon, using the Gaussian beam approximation. Optimal conditions for achievement of narrow spectral linewidth are discussed (location of the grating or of the beam expander). Various configurations of oscillator cavities are investigated, including a dispersive device composed of one grating and one virtual grating. The use of a beam expander is treated. We find that the same spectral linewidth is obtained theoretically for the optical cavity with two gratings as with one grating and a virtual grating. In the second part we describe the performance (in terms of spectral linewidth 1.3-GHz FWHM quasiunimodal structure, divergence of the beam, etc.) of the dye laser in light of the theoretical arguments. The complete laser contains an oscillator stage, a preamplifier stage, and an amplifier stage, each pumped by an UV beam (355 nm) from a pulsed Nd:YG laser.