We demonstrate a new generation of composition-tuned, ternary GaAsSb nanowire lasers on silicon with emission wavelengths tuned to below the Si bandgap. By solving previous limitations in the growth of III-As-Sb based nanowires, resonator cavities with extended lengths > 7 µm and high Sb-content (~30%) are realized as a base for bulk-type or quantum-well based nanowire lasers. Bulk GaAsSb nanowire lasers with high radiative efficiency and low threshold are enabled by use of lattice-matched InAlGaAs surface passivation layers. Coaxial InGaAs multi-quantum well (MQW) active regions grown on GaAsSb nanowire templates open further scope of tailoring material gain and lasing wavelength.
Continuous-wave (cw) operation of integrated nanoscale lasers is a key ingredient for on-chip optical processing schemes in Si photonic circuits. Here, we demonstrate cw-lasing from individual InAs nanowires at mid-infrared wavelengths (2.4-2.7 µm) without any external cavity for mode confinement. Using finite difference time domain (FDTD) modelling of the threshold gain, optimal single Fabry-Perot nanowire laser geometries with diameter > 800 nm and lengths of 10-30 µm are realized by site-selective growth methods. Corresponding nanowires exhibit cw-lasing with thresholds around 10-30 kW/cm2 at lasing emission up to 70K.
Nanowire lasers can be monolithically and site-selectively integrated onto silicon photonic circuits. To assess their full potential for ultrafast opto-electronic devices, a detailed understanding of their lasing dynamics is crucial. However, the roles played by their resonator geometry and the microscopic processes that mediate energy exchange between the photonic, electronic, and phononic systems are largely unexplored. Here, we apply femtosecond pump-probe spectroscopy to show that GaAs-AlGaAs core-shell nanowire lasers exhibit unexpected non-equilibrium dynamics occurring over few picosecond timescales. As we will show, these dynamics are intricately linked to the strong interaction between the lasing mode and the gain material arising from their wavelength-scale dimensions. We anticipate that our results will lead to new approaches for ultrafast intensity and phase modulation of chip-integrated nanoscale semiconductor lasers.
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