Investigation of passively synchronized dual-wavelength Q-switched lasers based on V:YAG saturable absorber J. Janousek * , P. Tidemand-Lichtenberg, J.L. Mortensen, P. Buchhave Department of Physics, Technical University of Denmark, Building 309, DK-2800 Lyngby, Denmark Received 13 May 2005; received in revised form 3 February 2006; accepted 1 March 2006 Abstract In this paper the results of a theoretical and experimental investigation of synchronized passive Q-switching of two Nd:YVO 4 -based solid-state lasers operating at two different wavelengths, is described. A V:YAG saturable absorbing material was used as a passive Q-switch performing the synchronization of the two laser fields. This material provides Q-switching operation at both 1064 and 1342 nm wavelengths simultaneously, saturating the same energy level. By adjusting the pump power of both lasers, it was possible to optimize the overlap of the two pulse trains and to switch between different states of synchronization. A theoretical model based on rate equations, which has been developed in order to investigate optical performance of the laser system, is in a good agreement with the experimental results. The principle of synchronized Q-switching can lead to new, pulsed all-solid-state light sources at new wave- lengths based on sum-frequency mixing processes. Ó 2006 Elsevier B.V. All rights reserved. PACS: 42.55.Xi; 42.60.Gd; 42.65.Sf Keywords: Lasers solid-state; Lasers Q-switched; Synchronization; V:YAG 1. Introduction Recent interest in efficient diode-pumped solid-state pulsed lasers in the yellow spectral region has led to a num- ber of interesting configurations, typically based on sum- frequency mixing of two pulsed infrared lasers. To obtain efficient conversion in the nonlinear process, the two laser pulses have to be synchronized very carefully. An active Q-switch working at both wavelengths simultaneously has previously been used to synchronize two lasers operat- ing at different wavelengths [1]. However, the overall laser system is rather complicated, costly and requires outside driving circuitry. Using a passive Q-switch for synchroniza- tion of two pulsed laser fields is more economical, main- taining compactness of the final laser system. In a previous publication [2], it was experimentally dem- onstrated that dual-wavelength synchronized Q-switching of two laser fields of different wavelengths based on Nd:YVO 4 as the active medium and using V:YAG as a saturable absorber is possible. V:YAG provides Q-switching operation at both 1064 and 1342 nm wave- lengths simultaneously [3,4], saturating the same energy level. Inserting a V:YAG saturable absorber into a common path of two lasers operating at 1064 and 1342 nm may therefore result in synchronized Q-switching of the two lasers. In this paper, a system operating in the synchronized state will be described both theoretically and experimentally. First, the experimental setup and facilities will be described. Next, the theoretical model based on rate equations is introduced and used to explain the effect of synchronized Q-switching. Finally, the experimental results will be presented and compared to the simulation. 0030-4018/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2006.03.002 * Corresponding author. Tel.: +4528257216; fax: +4545931669. E-mail address: janousek@fysik.dtu.dk (J. Janousek). www.elsevier.com/locate/optcom Optics Communications 265 (2006) 277–282