Institute of Optics, University of Rochester, Rochester, New York 14627, USA.
Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG 30123-970, Brazil.
Phys Rev Lett. 2014 Oct 31;113(18):186101. doi: 10.1103/PhysRevLett.113.186101. Epub 2014 Oct 28.
Inelastic light scattering in crystals has historically been treated as a spatially incoherent process, giving rise to incoherent optical radiation. Here we demonstrate that Raman scattering can be spatially coherent, in which case it depends on the dimensionality and symmetry of the scatterer. Using near-field spectroscopy, we measure a correlation length of ∼30 nm for the optical phonons in graphene, the results varying with vibrational symmetries and spatial confinement of the phonons.
晶体中的非弹性光散射在历史上一直被视为一种空间非相干过程，产生非相干光辐射。在这里，我们证明拉曼散射可以是空间相干的，在这种情况下，它取决于散射体的维度和对称性。我们使用近场光谱学测量了石墨烯中光学声子的相关长度约为 30nm，结果随声子的振动对称性和空间限制而变化。
