Ultrafast wavelength-dependent lasing-time dynamics in single ZnO nanotetrapod and nanowire lasers |
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Authors: | Song Jae Kyu Szarko Jodi M Leone Stephen R Li Shihong Zhao Yiping |
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Institution: | Department of Chemistry, and Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA. |
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Abstract: | The ultrafast lasing dynamics of single zinc oxide nanotetrapods and nanowires are investigated by two-color femtosecond excitation/optical injection spectroscopy. The transient spectral gain induced by time-delayed optical injection pulses (400 nm) is used to investigate the spectrally and temporally resolved lasing properties in a single tetrapod or nanowire laser excited by 267-nm pulses. The lasing output pulse exhibits a faster lasing decay time than the carrier decays due to the superlinear dependence of the lasing on the carrier density. Lasing at the low-energy side of the gain bandwidth (392 nm) has a full width at half maximum (fwhm) for stimulated emission of 1.7 ps. Lasing at 390 nm, the high-energy side of the gain bandwidth, has a fwhm of 2.1 ps for a single example nanowire. The change in lasing dynamics as a function of wavelength is affected by band gap renormalization, since lasing in the electron-hole plasma regime depends not only on the carrier density but also on the band gap shift with carrier density. |
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