Mode-locked VECSEL SESAM with intracavity antenna for terahertz emission

Mode-locked Vertical External-Cavity Surface-Emitting Lasers (ML-VECSELs) have seen advances in pulse energy and peak power thanks to improved power handling techniques and structure designs. The significant increase in gain and intra-cavity power, coupled with the VECSEL’s accessible external-cavity, has made the addition of intra-cavity elements for frequency conversion possible even for lossy conversion mechanisms. In this paper, we report a gold-patterned Semiconductor Saturable Absorbing Mirror (SESAM) that functions both as a slow saturable absorber in a ML-VECSEL and as an intracavity strip line Photo-Conductive Antenna (PCA) for THz emission. Here we describe the design of the strip emitter, THz-Time Domain Spectroscopy (TDS) performed with a ML-Yb fibre laser and the mode-locked characterisation of a ML-VECSEL built with the patterned SESAM.