Abstract
Brillouin and Raman scattering spectroscopy are established techniques for the nondestructive contactless and label-free readout of mechanical, chemical, and structural properties of condensed matter. Brillouin-Raman investigations currently require separate measurements and a site-matched approach to obtain complementary information from a sample. Here, we demonstrate a new concept of fully scanning multimodal microspectroscopy for simultaneous detection of Brillouin and Raman light scattering in an exceptionally wide spectral range, from fractions of GHz to hundreds of THz. It yields an unprecedented 150-dB contrast, which is especially important for the analysis of opaque or turbid media such as biomedical samples, and spatial resolution on a subcellular scale. We report the first applications of this new multimodal method to a range of systems, from a single cell to the fast reaction kinetics of a curing process, and the mechanochemical mapping of highly scattering biological samples.
- Received 21 February 2017
DOI:https://doi.org/10.1103/PhysRevX.7.031015
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
To study the molecular structure and dynamics of matter, researchers often target a focused beam of light on a sample and carefully analyze how that light scatters. Two techniques in particular, known as Raman and Brillouin spectroscopy, are the preferred choices for revealing chemical and mechanical information without disturbing the sample. Raman identifies local molecular vibrations while Brillouin reveals acoustic phonons (mechanical vibrations that propagate). When dealing with soft matter, and biological materials in particular, physicists often deal with samples that are heterogeneous and sometimes opaque, making it difficult to construct high-resolution maps. We present the design and test for a new instrument concept for simultaneous Brillouin and Raman microspectroscopy that operates in an exceptionally wide spectral range, with the high contrast and high resolution required for a variety of applications unapproachable by ordinary devices.
Our setup combines a Raman spectrometer with a multipass Fabry-Pérot interferometer. We demonstrate its performance with three case studies. First, we create in situ chemical and structural maps of biofilms, with the potential of revealing “persister cells,” which are among the major causes of hospital infections. Second, we monitor with subsecond time resolution mechanical and chemical changes in reacting materials. And third, we report the broadband detection of collective dynamics of biological matter, from fractions of gigahertz to hundreds of terahertz, with subcellular spatial resolution.
We expect that our device will move the frontiers of joint Brillouin-Raman spectroscopy forward by enabling applications in nontransparent media from photonic materials to biomedical samples.