Whispering gallery-mode lasing in ZnO microrods at room temperature

Abstract

An individual hexagonal ZnO microrod was employed as a whispering-gallery mode (WGM) microcavity to obtain ultraviolet lasing at room temperature. The WGM lasing shows a low threshold, a high quality factor, and distinct mode structure. A typical stimulated emission from the ZnO microrod with diagonal of 6.67 μm exhibits a low lasing threshold of 255 kW/cm2. The observed discrete lasing modes match with the simulated positions very well. The spatial distribution of the lasing intensity demonstrates the lasing output direction and provides the direct evidence of the WGM resonant mechanism. We systematically investigated the lasing performance for different sized microrods.

Whispering gallery modes in deformed hexagonal resonators

“…6) of a ZnO microwire (R ¼ 1.66 mm), fabricated by carbothermal evaporation. Also lasing modes are generally found to be of WGM type [29,31,42]. However, in Fig.…”

“…1) have been investigated in various material systems such as (Al,Ga)As/ GaAs [20], GaN [21], (In,Ga)N [22], ZnO [17,23,24], In 2 O 3 [25], and organic materials [26]. Stimulated emission (lasing) has been demonstrated for triangular [15,27], hexagonal [28][29][30][31][32], and dodecagonal [33] cavities.…”

Controllable fabrication and optical properties of Sn-doped ZnO hexagonal microdisk for whispering gallery mode microlaser

“…The Q factor of the microdisk cavity is comparable with that of the microrod. 14 The left inset of Figure 5(b) shows the integrated emission intensity versus excitation power density. The emission intensity increases slowly when the excitation power density is below 250 kW/cm 2 , and it increases rapidly when the excitation power density is larger than 250 kW/cm 2 .…”

“…[10][11][12][13][14][15][16][17][18][19] Most of the high quality WGM lasing results were observed from ZnO microrod/wires with several millimeters. [12][13][14][15][16] However, the traditional GaAs and GaN WGM microcavities are of disk structures formed by the etching technique. 20,21 It means that high performance thin film deposition system and etching machine are indispensable for fabricating ZnO microdisk WGM cavities.…”

Zinc Oxide Nanophotonics

“…In the case of resonators, the light is trapped inside the cavity by multiple total internal reflections at the interface near the structure and the surrounding medium, resulting in light circulation around the cavity in the inner walls of ZnO structures [67]. Due to a lower loss and better confinement, ZnO WGMs cavity is expected to demonstrate a high Q factor and relatively simple fabrication [68,69]. So far, WGMs have been observed in various ZnO nanostructures such as triangular [70], hexagonal [71], or dodecagonal [72] cross section.…”