Abstract

Passive Mode-Locking (PML) is arguably one of the most elegant methods to obtain short and intense pulses in the output of a laser. It is achieved by combining two elements, a laser amplifier providing gain, and a saturable absorber (SA) acting as a pulse shortening element. The different dynamical properties of the SA and of the gain can create a window for amplification only around the pulse, thus leading to a pulsed emission [1]. In semiconductor lasers, PML can be achieved by coupling Vertical External Cavity Surface-Emitting Lasers (VECSEL) with a Semiconductor Saturable Absorber Mirror [2]. The external cavity is designed to operate in the fundamental Gaussian mode since the presence of higher order transverse modes is usually perceived as detrimental for PML stability. Nevertheless, the possibility of achieving a cooperative effect of transverse modes for which they would contribute to longitudinal mode-locking is very attractive for increasing pulse power.

© 2015 IEEE