Vasileiadis Thomas, Zhang Heng, Wang Hai, Bonn Mischa, Fytas George, Graczykowski Bartlomiej
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznanskiego 2, 61-614 Poznan, Poland.
Sci Adv. 2020 Dec 18;6(51). doi: 10.1126/sciadv.abd4540. Print 2020 Dec.
Telecommunication devices exploit hypersonic gigahertz acoustic phonons to mediate signal processing with microwave radiation, and charge carriers to operate various microelectronic components. Potential interactions of hypersound with charge carriers can be revealed through frequency- and momentum-resolved studies of acoustic phonons in photoexcited semiconductors. Here, we present an all-optical method for excitation and frequency-, momentum-, and space-resolved detection of gigahertz acoustic waves in a spatially confined model semiconductor. Lamb waves are excited in a bare silicon membrane using femtosecond optical pulses and detected with frequency-domain micro-Brillouin light spectroscopy. The population of photoexcited gigahertz phonons displays a hundredfold enhancement as compared with thermal equilibrium. The phonon spectra reveal Stokes-anti-Stokes asymmetry due to propagation, and strongly asymmetric Fano resonances due to coupling between the electron-hole plasma and the photoexcited phonons. This work lays the foundation for studying hypersonic signals in nonequilibrium conditions and, more generally, phonon-dependent phenomena in photoexcited nanostructures.
电信设备利用高超音速千兆赫声子来介导微波辐射的信号处理，并利用电荷载流子来操作各种微电子元件。通过对光激发半导体中声子进行频率和动量分辨研究，可以揭示超高频声与电荷载流子之间的潜在相互作用。在此，我们提出一种全光学方法，用于在空间受限的模型半导体中激发和进行千兆赫声波的频率、动量和空间分辨检测。利用飞秒光脉冲在裸硅膜中激发兰姆波，并通过频域微布里渊光谱进行检测。与热平衡相比，光激发千兆赫声子的数量增加了百倍。声子光谱揭示了由于传播导致的斯托克斯 - 反斯托克斯不对称性，以及由于电子 - 空穴等离子体与光激发声子之间的耦合导致的强烈不对称法诺共振。这项工作为研究非平衡条件下的高超音速信号以及更广泛地研究光激发纳米结构中依赖声子的现象奠定了基础。
