We present our recent progress in the monolithic integration and epitaxial gain control of GaAs-based nanowire (NW) lasers on Si photonic platform. First, we describe the challenges in realizing vertical-cavity NW lasers on Si and SOI-based waveguides based on the stringent requirements for high gain, low-loss wave-guiding and coupling efficiency as illustrated by detailed numerical simulations. Consequently, we discuss bottom-up, epitaxial schemes for site-selective integration of individual GaAs NW lasers on planar Si and non-planar Si ridge waveguides under different geometries, demonstrating vertical-cavity NW lasers with remarkably low lasing threshold (< 20 µJ/cm2) and high spontaneous emission coupling factor (B > 0.2) under pulsed optical excitation. First experiments of individual NW-lasers with direct coupling of lasing emission into the underlying Si-ridge waveguides are also shown.
To further improve the threshold gain and lasing characteristics and achieve wavelength tunability, we further tailor the active gain media using low-dimensional systems embedded in the NW resonator cavity. Here, we particularly emphasize the challenges in the growth of GaAs-based cavities that incorporate coaxial GaAs-AlGaAs and InGaAs-AlGaAs multiple quantum well (MQW) heterostructures and illustrate even routes towards quantum-wire or quantum-dot based gain media. Finally, we provide a direct comparison of the lasing characteristics of 3D-bulk like GaAs NW lasers with coaxial NW-MQW heterostructure lasers, and show how the control of composition and structure of the MQW shifts the lasing emission to longer wavelengths.
Gregor Koblmüller, Thomas Stettner, Jochen Bissinger, Daniel Ruhstorfer, Michael Kaniber, Benedikt Mayer, and Jonathan J. Finley, "Challenges in the monolithic integration and epitaxial gain control of III-V nanowire lasers on silicon (Conference Presentation)," Proc. SPIE 10543, Quantum Dots and Nanostructures: Growth, Characterization, and Modeling XV, 1054302 (Presented at SPIE OPTO: January 29, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2300033.5751542773001.
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