Exploring ultrafast negative Kerr effect for mode-locking vertical external-cavity surface-emitting lasers

Abstract

We present analytical considerations of "self-mode-locked" operation in a typical vertical external-cavity surface-emitting laser (VECSEL) cavity geometry by means of Kerr lens action in the semiconductor gain chip. We predict Kerr-lens mode-locked operation for both soft-and hard-apertures placed at the optimal intra-cavity positions. These predictions are experimentally verified in a Kerr-lens mode-locked VECSEL capable of producing pulse durations of below 500 fs at 1 GHz repetition rate.

Measurements of nonlinear lensing in a semiconductor disk laser gain sample under optical pumping and using a resonant femtosecond probe laser

“…5 While saturable absorbers based on carbon nanotubes 11 and graphene 12 have both been demonstrated, SESAM mode-locking has dominated the field of high performance SDLs (whether using an independent SESAM or an integrated one as used in Mode-locked Integrated External Cavity Surface Emitting Lasers (MIXSELs) [13][14][15] ). Several demonstrations exist describing the so-called self-modelocked SDLs, [16][17][18][19][20][21][22][23][24] but as of yet none of these reports have provided an unambiguous explanation of the mechanism causing the reported behaviour. A large part of the problem is that nonlinear lensing in SDL gain samples is poorly understood.…”

Optically pumped VECSELs: review of technology and progress

“…Significant attention has also been devoted to the so-called 'self-mode-locking' that was first reported by Chen et al in 2011 [375]. In these cases, the physical mechanism for the saturable absorption has been credited to a possible Kerr effect in the VECSEL gain material [376], but several reports have been published on the topic that both support and contradict self-mode-locking [207,211,307,[377][378][379][380][381]. Most notably, Quarterman et al [207] measured a sufficiently large Kerr effect in a VECSEL structure to support Kerr-lens mode locking.…”

Recent advances in ultrafast semiconductor disk lasers

“…Another modelocking mechanism reported recently is the so-called self-mode-locked VECSEL or the KLM-VECSEL [103][104][105][106] . No apparent saturable absorber is used in these laser cavities, and a hard aperture is inserted in front of the OC or highly reflective end mirror.…”