Electrical-pumping spasing action from cross-stacked microwires

The realization of electrically pumped lasers at deep sub-micro and nanometer scale operating far beyond the diffraction limit is still a crucial goal in nanophotonics and plasmonics for prospective fundamental research and application. Herein, electrically pumped spasing action was captured from a cross-stacked architecture composed of a single Ga-doped ZnO microwire (ZnO:Ga MW) crossed with another ZnO:Ga MW covered by Au nanoparticles. To exploit the spasing feature, a plasmonic nanocavity could be constructed based on the sandwiched structures, with isolated Au nanoparticles filling the spacer between the crossed MWs. When both emission regions from the crossed MWs overlapped with each other, the cross-stacked architecture exhibited quasi-Schottky junction behavior, resulting in the formation of a tunneling junction. When the injection current exceeded certain values, bright and localizing emissions were observed at the crossed regions, with a sharp peak emerging in the emission spectra. The dominant emission wavelengths centered at 550 nm were accompanied by the spectral linewidth rapidly narrowing to 2 nm, suggesting a transition from spontaneous to stimulated emission. The electrically pumped lasing characteristics can be attributed to efficient metal plasmons amplification by the stimulated emission of radiation from Au nanoparticles, which filled the nanocavities. Therefore, this cross-stacked architecture provides a natural route towards electrical injection schemes that can be employed to construct electrical-pumping spasers. This technology also provides a candidate to investigate the fabrication of tunneling diodes.

在远超衍射极限的深亚微米和纳米尺度上实现电泵浦激光，对于纳米光子学和等离子体激元学的基础研究及应用前景而言，仍然是一个关键目标。在此，从由一根掺镓氧化锌微丝（ZnO:Ga MW）与另一根被金纳米粒子覆盖的ZnO:Ga MW交叉组成的交叉堆叠结构中，捕获到了电泵浦的受激辐射放大（spasing）行为。为了利用这种受激辐射放大特性，可以基于夹层结构构建一个等离子体纳米腔，在交叉的微丝之间的间隔中填充孤立的金纳米粒子。当交叉微丝的两个发射区域相互重叠时，交叉堆叠结构呈现出准肖特基结行为，从而导致隧道结的形成。当注入电流超过一定值时，在交叉区域观察到明亮且局域化的发射，发射光谱中出现一个尖锐的峰。中心位于550 nm的主发射波长伴随着光谱线宽迅速窄化至2 nm，这表明从自发发射到受激发射的转变。电泵浦激光特性可归因于填充纳米腔的金纳米粒子的受激辐射对金属等离子体的有效放大。因此，这种交叉堆叠结构为电注入方案提供了一种自然的途径，可用于构建电泵浦的受激辐射放大器（spasers）。这项技术也为研究隧道二极管的制造提供了一种可能。