Spectroscopy at the tip – CW tunable lasers and their use in TERS Raman spectroscopy
Photonics research undertakes considerable efforts to continuously refine nanoimaging techniques driven by the desire to characterize electronic and vibronic properties of new materials with nanometer resolution.
Tip-enhanced Raman spectroscopy (TERS) is an approach that has been well recognized and relies on strongly localized enhancement of Raman scattering of laser light at the point of a near atomically sharp tip. However, not least due to the lack of sources delivering laser light tunable throughout the visible spectral range, the vast majority of TERS experiments so far has been limited to single excitation wavelengths. A recent study demonstrates excitation-dependent hyperspectral imaging, exemplified on carbon nanotubes by implementing a tunable continuous-wave optical parametric oscillator into a TERS set-up. We take a closer look at the laser technology behind the experiment and illustrate the vast potential of the method.
Outlook
The experimental demonstration of excitation-tunable tipenhanced Raman spectroscopy comes in tandem with the availability of novel tunable laser light sources based on OPO technology. From the general laser technology point-of-view, the performance characteristics of OPOs make them competitive alternatives to conventional lasers and related technologies for the generation of widely tunable cw radiation. From the experimental methodology point-of-view, we expect e-TERS to open new experimental horizons for studying the electronic and vibronic properties of matter on the nanometer scale.
Read more: Spectroscopy at the tip
by Jaroslaw Sperling and Korbinian Hens of HÜBNER Photonics in Kassel, Germany (www.hubner-photonics.com)