Femtosecond high-power quantum dot vertical external cavity surface emitting laser

TLDR

The study reports the first femtosecond VECSEL exceeding 1 W average power and introduces a novel gain structure with flat GDD of ±10 fs² over 30 nm around 960 nm. The laser is an optically pumped, thin‑disk VECSEL using self‑assembled InAs quantum‑dot gain layers, passively modelocked with a fast QD‑SESAM, featuring a flat GDD of ±10 fs² over 30 nm, 63 optimally positioned QD layers for broadened gain, and a 500‑fs recovery time absorber, all sharing similar cavity mode areas to enable high repetition rates. The device delivers 1 W average power with 784‑fs pulses at 5.4 GHz, achieving a GDD several orders of magnitude lower than standard designs.

Abstract

We report on the first femtosecond vertical external cavity surface emitting laser (VECSEL) exceeding 1 W of average output power. The VECSEL is optically pumped, based on self-assembled InAs quantum dot (QD) gain layers, cooled efficiently using a thin disk geometry and passively modelocked with a fast quantum dot semiconductor saturable absorber mirror (SESAM). We developed a novel gain structure with a flat group delay dispersion (GDD) of ± 10 fs2 over a range of 30 nm around the designed operation wavelength of 960 nm. This amount of GDD is several orders of magnitude lower compared to standard designs. Furthermore, we used an optimized positioning scheme of 63 QD gain layers to broaden and flatten the spectral gain. For stable and self-starting pulse formation, we have employed a QD-SESAM with a fast absorption recovery time of around 500 fs. We have achieved 1 W of average output power with 784-fs pulse duration at a repetition rate of 5.4 GHz. The QD-SESAM and the QD-VECSEL are operated with similar cavity mode areas, which is beneficial for higher repetition rates and the integration of both elements into a modelocked integrated external-cavity surface emitting laser (MIXSEL).