Experimental comparison of extended-cavity passively mode-locked 1.5 μm quantum well lasers with anti-colliding design and self-colliding design

In this paper we present an experimental verification of a prediction of significantly improved performance of an integrated passive mode-locked laser (PMLL) through the use of an anti-colliding (AC) design comparing with a self-colliding (SC) scheme. The most commonly used design is the linear SC cavity. In this scheme a saturable absorber (SA) is placed close to the high reflectivity facet, which allows the pulse to interact with itself within the SA. However in [1] it was shown theoretically that an AC design where the SA is placed next to the low reflectivity output coupler is advantageous. It leads to a higher stability, an increase of optical output power and shorter pulses due to the weaker saturation of the gain and enhanced modulation of the SA in comparison with symmetrical mode-locking (SML) and SC scheme. A marked improvement in the performance of two-section cleaved facet PMLLs was achieved by the introduction of a low-reflectance coating at the SA facet and a high-reflectance coating on the other facet in comparison with a non-coated device (SML configuration) in [2]. However, the deposition of the coatings may lead to changes in the reflection spectrum.