Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 95: Quantum Dots and Wires: Optical Properties III (mainly Cavities and Ultrafast Response)

HL 95.8: Talk

Friday, March 30, 2012, 11:15–11:30, EW 201

Low lasing threshold of CdS nanowires — •Robert Röder, Sebastian Geburt, and Carsten Ronning — Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena

Semiconductor nanowires mark the physical size limit for photonic lasers: a further miniaturization can only be achieved by combination of photonic with plasmonic structures. High quality cadmium sulfide nanowires (CdS NW) were synthesized via vapor-liquid-solid (VLS) mechanism. The intense near band edge emission and the minor defect emission at low excitation power indicate the marginal defect concentration. Sharp peaks evolving at moderate excitation powers dominate the luminescence spectrum at higher laser power. The evaluated power dependency clearly shows all characteristics of lasing action in the NW cavity. The low threshold of 10 kW/cm² at room temperature was observed as well as its relation to the Q factor of the cavity. The length of the NW resonator was examined as one determining factor for the high Q values of up to 1800. Polarization and angular distribution of the emission from one end of the optically pumped NW can be studied using a "head on" experimental configuration. The lower length and diameter limits for photonic NW lasing were evaluated, but the CdS nanolaser can generate highly localized intense monochromatic light ideally suited for coupling plasmonic structures such as metallic nanoparticles, plasmonic substrates and quantum dots.