Electron-hole plasma lasing in a ZnO random laser

Double threshold behavior in a resonance-controlled ZnO random laser

“…Because our proposed RLs can realize low-threshold and single-mode random lasing, which are quite distinct from conventional RLs, the photophysical phenomena related to ZnO excitons that are difficult to observe in conventional RLs could also be induced even in random structures, due to the improvement of photon localization by the use of resonant scatterers. In fact, in our previous study, 13 measuring the temperature dependence of the resonance-controlled RL properties, we found that the lasing origin was quite different from conventional RLs and suggested the possibility that the resonance-controlled RLs were related to exciton lasing, like well-designed microcavities, [21][22][23] whereas the origin of conventional ZnO RLs was caused by EHP recombination. 13,26 In this study, we observe the peculiar features (double threshold behavior, blue peak shift, and peak width change) of single-mode lasing in the resonance-controlled ZnO RL.…”

“…In fact, in our previous study, 13 measuring the temperature dependence of the resonance-controlled RL properties, we found that the lasing origin was quite different from conventional RLs and suggested the possibility that the resonance-controlled RLs were related to exciton lasing, like well-designed microcavities, [21][22][23] whereas the origin of conventional ZnO RLs was caused by EHP recombination. 13,26 In this study, we observe the peculiar features (double threshold behavior, blue peak shift, and peak width change) of single-mode lasing in the resonance-controlled ZnO RL. These features are similar to the polariton lasers and have been never before reported in conventional RLs.…”

“…So far, as gain materials, many studies on UV ZnO lasers have also been reported in various micro-/nano-cavity structures, such as random structures, [1][2][3][4][5][6][7][8][9][10][11][12][13] Fabry-Perot cavities, [14][15][16][17] whispering-gallery-mode resonators. [18][19][20][21] Although, in most of these ZnO lasers, the gain from electron-hole plasma (EHP) recombination under high excitation intensity condition has typically been reported as the origin of the stimulated emission (photon lasing), 12,13 the lasing originated by excitonic recombination, so-called polariton/exciton lasers, has also been demonstrated in well-designed cavity structures at room temperature. [21][22][23] Random lasers (RLs) based on photon localization due to multiple light scattering have been reported in various materials.…”

“…In particular, because ZnO has the above-mentioned advantages and high gain, there are numerous studies on RLs so far. [1][2][3][4][5][6][7][8][9][10][11][12][13] In typical random structures, because localized modes are spontaneously formed and its modal control is difficult due to the multiple light scattering, the lasing peak wavelengths depend mainly on the property of gain materials and their thresholds are determined by the mean scattering property of the structure. Furthermore, the features of the RL (e.g., multimode lasing and high thresholds) make it difficult to realize strong interactions between cavity modes and gain materials and observe cavity-related phenomena, [21][22][23][24] like observed in well-designed resonators, as mentioned above.…”

Double threshold behavior in a resonance-controlled ZnO random laser

“…This indicates that the lasing origin above 2nd thresholds is considered to be EHP recombination, as similar to conventional RLs. 13,26 Even though the same lasing origin as EHP recombination, the 2nd threshold value is lower than those of conventional RLs. We also should note that the n th of 2nd threshold is clearly lower than n g .…”