Recent Innovations in Nanoscale IR Spectroscopy: A Tunable Broadband IR Laser Source for Near-Field Imaging and Spectroscopy

The properties of chemically or structurally heterogeneous materials are often determined by intermolecular interactions over nanometer length scales. Measurement tools that can access these length scales with chemical specificity are thus highly desirable in understanding and engineering many advanced materials.
Broadband infrared scattering scanning near-field optical microscopy (IR s-SNOM) is one of such technique that can perform chemical imaging and nanoFTIR spectroscopy with the desired spatial resolution and chemical specificity. Based on the scattering response of a sample coupled in the near-field to the plasmonic enhancement of a metalized scanning probe tip, IR s-SNOM is broadly compatible with a variety of laser sources (like QCLs, broadband lasers etc.) and detection modalities.
In the presentation we demonstrate an ultra-broadband (6 octave) nano spectroscopy platform by combining a high power mid-IR OPO/DFG laser source with an IR s-SNOM system. Due to the architecture of the broadband laser source, it allows the unique combination to perform 200 cm-1 broadband emission over a wavenumber range from 4000-670 cm-1 and 20 cm-1 narrowband operation over the 2000-670 cm-1 wavenumber range. Apart from the quasi-cw operation of the broadband IR source which is required for s-SNOM measurements, additionally a triggered pulsed mode is available for photothermal AFM-IR investigations. Therefore, in terms of flexibility and tuning range the OPO/DFG laser source sets a new standard for the complementary nanoscale IR techniques, especially IR s-SNOM spectroscopy (nano-FTIR) and imaging and photothermal AFM-IR.
In this context, we will also highlight the laser performance and will demonstrate its use on several samples which will achieve promising new insights in the understanding of a multitude of different materials.