Phonon-assisted lasing in ZnO microwires at room temperature

Abstract

We report on room temperature phonon-assisted whispering gallery mode (WGM) lasing in ZnO microwires. For WGM laser action on the basis of the low gain phonon scattering process high quality resonators with sharp corners and smooth facets are prerequisite. Above the excitation threshold power P Th of typically 100 kW/cm 2 , the recombination of free excitons under emission of two longitudinal optical phonons provides sufficient gain to overcome all losses in the microresonator and to result in laser oscillation. This threshold behavior is accompanied by a distinct change of the far and near field emission patterns, revealing the WGM related nature of the lasing modes. The spectral evolution as well as the characteristic behavior of the integrated photoluminescence intensity versus the excitation power unambiguously prove laser operation. Polarization-resolved measurements show that the laser emission is linear polarized perpendicular to the microwire axis (TE).

Extinction of the zero-phonon line and the first-order phonon sideband in excitonic luminescence of ZnO at room temperature: the self-absorption effect

“…In fact, all reported room-temperature TPA-PL spectra of various ZnO always peak at $390 nm [7,15,[21][22][23][24]. Even for all laser spectra of various forms of ZnO at room temperature, their spectral centers always located at $390 nm [1][2][3][4][5][6][8][9][10][11][12][13][14][15][16][17][22][23][24][25]. These highlyconsistent experimental data from different groups indicate that someone unified mechanism shall be responsible for the phenomenon.…”

“…Moreover, Klingshirn pointed out the possible influence of selfabsorption (SA) effect on the laser signatures of ZnO for the first time. Nowadays, the LO phonon-assisted laser mechanism in ZnO at room temperature has been well established [16,17]. However, there have been very few rigorous studies devoted to examining the SA effect in luminescence and laser emission of ZnO, so that until now, the large redshift in laser and spontaneous emission at room temperature remains as a mystery.…”

SiO2 substrate and Mo,In codoping effect on crystalline and vibrational characteristics of ZnO sprayed thin films

“…Those characteristic modes of high unicity and polarity of ZnO Wurtzite [36,42,46] are highly valued for optoelectronic applications of single or double emission and have been investigated by different techniques in the literature [46][47][48].…”

Review on the dynamics of semiconductor nanowire lasers

“…Instead, the photo-excited carriers including excitons start to interact with each other, such that elastic and inelastic scattering processes can occur [43]. These high excitation processes can indeed cause stimulated recombination processes [45], which includes exciton-exciton (X-X) (or polariton-polariton) scattering in II-VI compounds [46][47][48], and III-V compounds [49,50], exciton-electron (hole) (X-e[h]) scattering [45] and exciton-phonon (X-nLO) processes [51]. However, it has become widely accepted that these processes in most cases do not provide enough optical gain in order to ensure lasing in NW FP cavities according to equation (1).…”