Spatial coherence in near-field Raman scattering.
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.
Institute of Optics, University of Rochester, Rochester, New York 14627, USA.
Ryan
R
Beams
Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG 30123-970, Brazil.
Luiz Gustavo
LG
Cançado
Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Sang-Hyun
SH
Oh
Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG 30123-970, Brazil.
Ado
A
Jorio
Photonics Laboratory, ETH Zürich, 8093 Zürich, Switzerland*
Lukas
L
Novotny