Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
Nat Commun. 2011 Jul 26;2:403. doi: 10.1038/ncomms1412.
Stimulated Brillouin interaction between sound and light, known to be the strongest optical nonlinearity common to all amorphous and crystalline dielectrics, has been widely studied in fibres and bulk materials but rarely in optical microresonators. The possibility of experimentally extending this principle to excite mechanical resonances in photonic microsystems, for sensing and frequency reference applications, has remained largely unexplored. The challenge lies in the fact that microresonators inherently have large free spectral range, whereas the phase-matching considerations for the Brillouin process require optical modes of nearby frequencies but with different wave vectors. Here we rely on high-order transverse optical modes to relax this limitation and report the experimental excitation of mechanical resonances ranging from 49 to 1,400 MHz by using forward Brillouin scattering. These natural mechanical resonances are excited in ∼100 μm silica microspheres, and are of a surface-acoustic whispering-gallery type.
受激布里渊相互作用是一种常见于所有非晶态和晶态电介质的最强光学非线性现象，它在光纤和块状材料中得到了广泛的研究，但在光学微谐振器中却很少见。将这一原理应用于激发光子微系统中的机械共振，以实现传感和频率参考应用的实验可能性，在很大程度上仍未得到探索。挑战在于微谐振器本身具有很大的自由光谱范围，而布里渊过程的相位匹配要求光学模式的频率相近，但波矢不同。在这里，我们依赖于高阶横向光学模式来放宽这一限制，并报告了通过前向布里渊散射实验激发的机械共振，频率范围从 49MHz 到 1400MHz。这些自然机械共振是在约 100μm 的二氧化硅微球中激发的，属于表面声波的 whispering-gallery 类型。
