Quantum - dot external - cavity passively mode - locked laser with high peak power and pulse energy

An InAs quantum-dot external-cavity passively mode-locked laser with an operation wavelength of 1.27 μm is demonstrated, based on a two-section quantumdot superluminescent diode with bending ridge waveguide and a 96% output coupler. Stable mode-locking with an average power up to 60 mW was obtained at a repetition frequency of 2.4 GHz. This performance corresponds to a 25-pJ pulse energy obtained directly from the oscillator, which represents a 55-fold increase in the pulse energy when compared to the current state-of-the-art for semiconductor lasers. At a repetition frequency of 1.14 GHz, picosecond optical pulses with 1.5-W peak power are also demonstrated, representing the highest peak power achieved from an external-cavity laser at the 1.3 μm waveband, without the use of any pulse compression or optical amplification. Introduction: High-power, electrically-pumped mode-locked semiconductor lasers generating picosecond pulse trains have been regarded as potentially suitable for a wide variety of applications, such as optical clocking, telecommunications, nonlinear optics and biomedical applications [1-3]. Mode-locked lasers based on quantum-dot (QD) materials present a number of significant advantages such as ultrafast absorption recovery, broad gain bandwidth and low threshold current density. This latter characteristic, together with low optical losses, enables the fabrication of long-cavity and extremely high wall-plug efficiency lasers [4-6].