Ultra-small mode area V-groove waveguide design for on-chip single-photon emission.

We numerically investigate the figures of merit for single-photon emission in a planar GaAs-on-insulator waveguide featuring a V-groove geometry. Thanks to a field enhancement effect arising due to boundary conditions of this waveguide, the structure features an ultra-small mode area enabling a factor of a maximum 2.8 times enhancement of the Purcell factor for quantum dot and a more significant 7 times enhancement for the atomic-size solid-state emitters with the aligned dipole orientation. In addition, the coupling efficiency to the fundamental quasi-TE mode is also improved. To take into account potential on-chip integration, we further show that the V-groove mode profile can be converted using a tapering section to the mode profile of a standard ridge waveguide while maintaining both the high Purcell factor and the good fundamental mode coupling efficiency.

Effect of p-doping on the intensity noise of epitaxial quantum dot lasers on silicon.

This work experimentally investigates the impact of p-doping on the relative intensity noise (RIN) properties and subsequently on the modulation properties of semiconductor quantum dot (QD) lasers epitaxially grown on silicon. Owing to the low threading dislocation density and the p-modulation doped GaAs barrier layer in the active region, the RIN level is found very stable with temperature with a minimum value of -150dB/Hz. The dynamical features extracted from the RIN spectra show that p-doping between zero and 20 holes/dot strongly modifies the modulation properties and gain nonlinearities through increased internal losses in the active region and thereby hinders the maximum achievable bandwidth. Overall, this Letter is important for designing future high-speed and low-noise QD devices integrated in future photonic integrated circuits.

High optical feedback tolerance of InAs/GaAs quantum dot lasers on germanium.

This work experimentally investigates the optical feedback sensitivity of InAs/GaAs quantum dot (Qdot) lasers epitaxially grown on Ge substrate. In comparison with a Qdot laser on GaAs substrate with identical epilayer and cavity structures, the Ge-based laser is found to exhibit lower sensitivity to the optical feedback, although it has a higher epitaxial defect density. Theoretical analysis proves that the high defect density strongly increases the damping factor while slightly reduces the linewidth broadening factor, which lead to high tolerance to the optical feedback. This work suggests the high potential of Qdot lasers on Ge for isolator-free operation in photonic integrated circuits.