光学声子的参量放大
Parametric amplification of optical phonons
摘要：
通过受激发射或非线性光学相互作用对光的放大对现代科学和技术产生了变革性的影响。其他玻色子激发的放大，如固体中的声子，可能会开辟新的显着的物理现象。在这里，我们报告的光学声子放大的实验演示。利用相干中红外光场驱动碳化硅中Si-C伸缩模的大振幅振荡。在非线性声子激发时，第二探测脉冲在整个reststrahlen带的所有波长处经历参量光学增益，这反映了光学声子波动的放大。从第一性原理计算出发，我们证明了高频介电常数和声子振子强度与晶格坐标的平方关系。在这里探索的实验条件下，这些振荡然后在两倍的光场的频率，并提供了一个参数驱动晶格波动。声子四波混频中的参量增益是一种通用的机制，可以推广到固体的所有极性模，作为控制相变动力学、放大多体相互作用或控制声子-极化激元波的新手段。
英文摘要：
Amplification of light through stimulated emission or nonlinear optical interactions has had a transformative impact on modern science and technology. The amplification of other bosonic excitations, like phonons in solids, is likely to open up new remarkable physical phenomena. Here, we report on an experimental demonstration of optical phonon amplification. A coherent mid-infrared optical field is used to drive large amplitude oscillations of the Si-C stretching mode in silicon carbide. Upon nonlinear phonon excitation, a second probe pulse experiences parametric optical gain at all wavelengths throughout the reststrahlen band, which reflects the amplification of optical-phonon fluctuations. Starting from first principle calculations, we show that the high-frequency dielectric permittivity and the phonon oscillator strength depend quadratically on the lattice coordinate. In the experimental conditions explored here, these oscillate then at twice the frequency of the optical field and provide a parametric drive for lattice fluctuations. Parametric gain in phononic four wave mixing is a generic mechanism that can be extended to all polar modes of solids, as a new means to control the kinetics of phase transitions, to amplify many body interactions or to control phonon-polariton waves.
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