Mitsubori S, Katayama I, Lee SH, Yao T, Takeda J. Ultrafast lasing due to electron-hole plasma in ZnO nano-multipods.
JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009;
21:064211. [PMID:
21715913 DOI:
10.1088/0953-8984/21/6/064211]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Dynamics of stimulated emission and ultrafast lasing in ZnO nano-multipods has been investigated with a femtosecond optical Kerr shutter technique. Under band-to-band excitation with high density, stimulated emission is observed around 395-400 nm with a mode-like structure. The stimulated emission emerges with an onset time of ∼2 ps and then the intensity gradually decreases with time having a blue-shift and a spectral narrowing. The characteristics of the blue-shift and spectral narrowing suggest that not only recovery of bandgap renormalization but also conversion from an electron-hole plasma (EHP) state to high density excitonic state takes place as the carrier density decreases due to recombination of electrons with holes. The mode-like structure observed strongly indicates that a high quality resonant cavity is formed between the two facets toward the leg length direction of individual nano-multipod. These results show that the ultrafast lasing observed around 395-400 nm in ZnO nano-multipods comes from population inversion in the EHP regime. We also found that the initial carrier distribution of the EHP regime in nano-multipods is much wider than that in ZnO thin films, implying that the carrier diffusion might be suppressed by their nano-size structure.
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