1.34  μm VECSEL mode-locked with a GaSb-based SESAM

Mode locking of a 1.34 μm vertical external cavity surface emitting laser is demonstrated using a GaSb-based semiconductor saturable absorber mirror (SESAM). The SESAM includes six AlGaSb quantum wells (QWs) with an absorption edge at ∼1.37  μm. The proposed approach has two key benefits: the QWs can be grown lattice matched, and only a small number of Bragg reflector layers is required to provide high reflectivity. Pump–probe measurements also reveal that the AlGaSb/GaSb structure exhibits an intrinsically fast absorption recovery on a picosecond timescale. The mode-locked laser pulse train had a fundamental repetition rate of 1.03 GHz, a pulse duration of ∼5  ps, and a peak power of ∼1.67  W. The demonstration paves the way for exploiting GaSb-based SESAMs for mode locking in the 1.3–2 μm wavelength range, which is not sufficiently addressed by GaAs and InP material systems.