Ultrabroadband Nanospectroscopy with a Laser-Driven Plasma Source

Abstract

Scattering-type scanning near-field optical microscopy (s-SNOM) enables infrared spectroscopy at 10–20 nm spatial resolution through elastic light scattering. Coupled with an infrared light source, s-SNOM characterizes chemical compositions or probes nanoscale photonic phenomena on length scales 2 orders of magnitude below the diffraction limit. However, widespread use of s-SNOM as an analytical standard tool has been restrained to a large extent by the lack of a bright and affordable broadband light source. Here we present a turnkey thermal emitter based on a laser-driven plasma that offers incoherent radiation of a broader bandwidth (>1000 cm–1) and ∼40-fold higher brilliance than previous blackbody radiators in addition to a compact size and at a fraction of the cost of alternative coherent laser systems or synchrotrons. We demonstrate a nearly 1 order of magnitude increase in signal-to-noise in near-field spectra compared to existing incoherent emitters, which allows probing of not only inorganic materials and polaritonic systems but also various commonly used polymers despite their weak near-field optical response. The latter important representative of soft matter was previously inaccessible by table-top thermal radiators. s-SNOM combined with the laser-driven plasma will provide a widely accessible platform for infrared nanospectroscopy.