Abstract
For the first time a detailed study of hybrid mode-locking in two-section InAs/InP quantum dot Fabry-Pérot-type lasers is presented. The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses. The mechanism leading to this typical pulse shape and the phase noise is investigated by detailed radio-frequency and optical spectral studies as well as time-domain studies. The pulse shaping mechanism in these lasers is found to be fundamentally different than the mechanism observed in conventional mode-locked laser diodes, based on quantum well gain or bulk material.
Highlights
Mode-locking of laser diodes is a well-established technique for generating short optical pulses at wavelengths around 1.55 μm
For the first time a detailed study of hybrid mode-locking in twosection InAs/InP quantum dot Fabry-Pérot-type lasers is presented
The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses
Summary
Mode-locking of laser diodes is a well-established technique for generating short optical pulses at wavelengths around 1.55 μm. An overview of mode-locked quantum dot lasers can be found in [11] Many of these advantages have been reported with two-section MLLDs containing an optical amplifier and saturable absorber section, that are based on In(Ga)As/GaAs QD gain material. These lasers operate in the 1.2-μm to 1.3-μm wavelength region [12,13]. Hybrid mode-locking is defined as adding an electrical modulation, with a frequency close to the cavity free-spectral range, to a reversely biased intra-cavity saturable absorber (SA) section This is unlike active modelocking, where (part of) the gain section of the laser is modulated [20,21].
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