Ultrafast Dynamics of Lasing Semiconductor Nanowires
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- 作者：Robert R枚der ; Themistoklis P. H. Sidiropoulos ; Christian Tessarek ; Silke Christiansen ; Rupert F. Oulton ; Carsten Ronning
- 刊名：Nano Letters
- 出版年：2015
- 出版时间：July 8, 2015
- 年：2015
- 卷：15
- 期：7
- 页码：4637-4643
- 全文大小：439K
- ISSN：1530-6992
文摘
Semiconductor nanowire lasers operate at ultrafast timescales; here we report their temporal dynamics, including laser onset time and pulse width, using a double-pump approach. Wide bandgap gallium nitride (GaN), zinc oxide (ZnO), and cadmium sulfide (CdS) nanowires reveal laser onset times of a few picoseconds, driven by carrier thermalization within the optically excited semiconductor. Strong carrier鈥損honon coupling in ZnO leads to the fastest laser onset time of 鈭? ps in comparison to CdS and GaN exhibiting values of 鈭?.5 and 鈭?.5 ps, respectively. These values are constant between nanowires of different sizes implying independence from any optical influences. However, we demonstrate that the lasing onset times vary with excitation wavelength relative to the semiconductor band gap. Meanwhile, the laser pulse widths are dependent on the optical system. While the fastest ultrashort pulses are attained using the thinnest possible nanowires, a sudden change in pulse width from 鈭? to 鈭?5 ps occurs at a critical nanowire diameter. We attribute this to the transition from single to multimode waveguiding, as it is accompanied by a change in laser polarization.