Ultrafast Upconversion Probing of Lasing Dynamics in Single ZnO Nanowire Lasers

Abstract

The ultrafast lasing dynamics of single zinc oxide nanowires are studied by time-resolved upconversion of the lasing emission as a function of the ultraviolet excitation intensity. Induction times for stimulated emission in individual nanowires are observed to be 1-5 ps or 3-15 roundtrips for nominal 20 µm long nanowires, depending on the 267 nm excitation intensity. In separate experiments, transient absorption profiles are also obtained for time-delayed 800 and 400 nm pulses to elucidate the carrier dynamics, such as rapid decay (2-3 ps) of the electron-hole plasma (EHP) states at high carrier densities during lasing in the nanowire and the slower exciton decay component (15-60 ps) at lower excitation densities. The dynamics of the lasing wavelength dependence on carrier density is also studied and related to the band gap renormalization in the EHP regime.

Room-Temperature Laser Emission of ZnO Nanowires Explained by Many-Body Theory

“…[18]. We find that the vast majority of reported laser thresholds [5][6][7][8][9]12,13,[27][28][29][30][31][32] actually lie above the Mott density, between 1:5 Â 10 24 m À3 and 1:5 Â 10 26 m À3 . Only one group reported a lower threshold [3,4,24].…”

“…Here, it has often been stated that the lasing is due to scattering processes that involve excitons, at least, if the excitation intensity is not too far above the laser threshold [3][4][5][6][7][8][9][10][11][12][13][14]. Excitons are hydrogen-atom-like electron-hole pairs, bound by the Coulomb force.…”

“…Above the so-called ''Mott density,'' excitons cease to exist, and the charge carriers form an electronhole plasma. Indeed, in case excitation is far above laser threshold, lasing is claimed to make a transition from excitonic lasing to electron-hole plasma lasing [4,6,7,9,11,14]. On the other hand, Klingshirn et al [17] argue that excitons are probably not involved in most cases of room-temperature lasing in ZnO, even not just above threshold.…”

Handwriting enabled harvested piezoelectric power using ZnO nanowires/polymer composite on paper substrate

“…This is one of the reasons why ZnO has attracted a lot of interest for developing nanogenerators [1]. The synthesis of aligned ZnO NW arrays has been studied [9,10] during the past several years due to the various potential applications of aligned ZnO NW arrays in light emitting diodes [11][12][13], lasers [14,15], solar cells [16][17][18], nanogenerators [19][20][21] and piezotronics [22,23], etc. Various methods have been reported for synthesizing ZnO NW arrays, mainly including physical vapor phase transport and deposition [24][25][26], metal organic chemical vapor deposition (MOCVD) [27,28] and the low temperature hydrothermal approach [29][30][31].…”

Synthesis of different ZnO nanostructures by modified PVD process and potential use for dye-sensitized solar cells

“…It has an energy band-gap of 3.37 eV and an exciton binding energy of approximately 60 meV, characteristics that make possible its use for different electronic devices as diodes, field-effect transistors, conductometric sensors and dye-sensitized solar cells [11][12][13][14][15][16]1,8,9]. Nowadays, several techniques are being used to synthesize different nanostructures of this material; sol-gel and hydrothermal methods [7,1,6,4,9,5,17], chemical vapor deposition [18][19][20][21][22][23][24] and physical vapor deposition [25,26,2].…”