Abstract

We have recently experimentally verified that the Brewster-angle-cut Ti:S crystal acts as a biréfringent filter in a bare cavity without additional tuning elements.¹ Previously, Piché and coworkers² suggested that the birefringence of the Ti:S crystal could lead to a coupled-cavity effect and this can be used for mode-locking. This mechanism was also thought to aid in the production of pulses with width shorter than expected by an actively mode-locked Ti:S laser.³ The use of the intensity dependent rotation of the polarization ellipse of intra-cavity Kerr material for mode-locking has been reported by a number of authors.^3-5 These results suggest that the birefringence effect must be taken into account to understand the pulse-forming mechanisms of passively mode-locked Ti:S lasers. This is demonstrated conclusively for the first time in this paper.

© 1994 Optical Society of America