Active Mode Stabilization of Synchronously Pumped Dye Lasers

Abstract

Synchronously pumped mode-locked dye lasers have proved to be a reliable way of producing ultrashort light pulses throughout the visible region of the spectrum. Dramatic improvements in pulse duration have resulted from the use of rf generators of high spectral purity and very fine control of the dye laser cavity length with respect to the pump laser. However, synchronously pumped dye lasers have not yet reached the extremely short pulse duration typical of passive systems and appear to suffer from more timing jitter than their passive counterparts. We have explored methods of improving the properties of synchronously pumped dye lasers which are common in single mode dye lasers [1]. We expect such stabilization schemes to give rise to shorter, cleaner and more coherent pulse trains with less timing jitter. Many other stabilization methods have been proposed and demonstrated [2, 3, 4, 5]. These schemes attempt either to stabilize the ion pump laser or to stabilize the dye laser. It is clearly crucial that the pump laser must first be stabilized before the dye laser can be operated at its best and indeed most of the efforts have been directed at improving the pump laser. In this paper we propose and demonstrate a stabilization scheme which is applied to the dye laser only. The scheme can be applied to any mode-locked laser and has particular utility in experiments where the phase coherence of the pulse train is important. We have demonstrated the use of a stabilized dye laser in performing coherent multiple pulse Doppler-free spectroscopy. This source should also be ideal for coherent transient experiments using multiple pulse interactions [6].