## 2 Materials and Methods  
Figure 1a,b show a schematic cross-sectional diagram and scanning electron microscope (SEM) image of the InAs/InP F-P QDot SSP MLL with a single lateral mode ridge-waveguide structure. The laser structure was grown on a 3\" (001) oriented n-type InP substrate, with the n-type cladding and laser core grown by chemical beam epitaxy. An n-type InP cladding was first grown, followed by a 350 nm thick lattice matched InGaAsP waveguide core. The composition of InGaAsP was chosen to have a photoluminescence peak of 1.15 \(\upmu\)m at 300 K. This core structure provides both carrier and optical confinement. By choosing appropriated growth conditions we could create either QDot or QDash layers as the gain medium [37] in the waveguide core. For this device, we grew five stacked layers of QDots in the center, forming the laser active region. A top view SEM image of typical surface InAs Qdot is shown Figure 1c. The five InAs dot layers were deposited, followed by a 25 s growth interruption for each layer to allow the In to diffuse on the surface and form dots. Each dot layer is then capped with a thin InP barrier layer and finally capped with the InGaAsP barrier material. This double-cap process was used to precisely control the emission wavelength [29]. The average QDot density in each active layer is around \(3.5\times 10^{10}\) cm\({}^{-2}\). An upper p-type InP cladding layer (containing an etch stop for ridge fabrication) and a heavily doped p-type InGaAs contact layer are then grown with metal organic chemical vapor deposition.  
Following growth, lasers are processed by defining ridges using a combination of dry etching into the InP cladding followed by wet etching to an etch stop layer as shown in Figure 1a. Finally, a SiO2/SiN isolation layer and a metal contact layer are deposited to form a low resistance Ohmic contact. Devices are then cleaved to cavity lengths of 1500 \(\upmu\)m to form F-P lasers with a corresponding to 28.4 GHz mode spacing (repetition rate). A cleaved cross-section SEM image is shown in Figure 1b showing a waveguide width of 2.3 \(\upmu\)m. No coatings were deposited on the cleaved facets.  
For the experimental characterization the laser chip is mounted onto a commercially available aluminum nitride carrier to provide mechanical support with two gold electroplated pads to provide electrical connection to the laser chip. The laser chip is bonded substrate side down to one pad using eutectic gold tin, and the top contact is made through wire-bonding to the other pad. To reduce temperature fluctuations, this chip-on-carrier is placed on a copper block with a thermoelectric cooler underneath to maintain an operating temperature range of 18-20 \({}^{\circ}\)C. An ultra-low-noise battery powered laser diode driver controller (ILX Lightwave, Model LDC-3722) is used to DC bias the laser. The laser output light is collected from its front facet using a lensed polarization maintaining (PM) fiber attached to a two-stage PM isolator for reducing any back-reflections. The position of this lensed fiber is precisely adjustable in three dimensions for coupling the light optimally from the laser cavity. This laser is free run without any form of feedback to control the laser linewidth.