Unlocking the true potential of optical spectroscopy on the nanoscale requires development of stable and low-noise laser sources. Here, we have developed a low-noise supercontinuum (SC) source based on an all-normal dispersion fiber pumped by a femtosecond fiber laser and demonstrate high resolution, spectrally resolved near-field measurements in the near-infrared (NIR) region. Specifically, we explore the reduced-noise requirements for aperture-less scattering-type scanning near-field optical microscopy (s-SNOM), including inherent pulse-to-pulse fluctuation of the SC. We use our SC light source to demonstrate the first NIR, spectrally resolved s-SNOM measurement, a situation where state-of-the-art commercial SC sources are too noisy to be useful. We map the propagation of surface plasmon polariton (SPP) waves on monocrystalline gold platelets in the wavelength region of 1.34-1.75 μm in a single measurement, thereby characterizing experimentally the dispersion curve of the SPP in the NIR. Our results represent a technological breakthrough that has the potential to enable a wide range of new applications of low-noise SC sources in near-field studies.
Bibliographical noteFunding Information:
We acknowledge funding from European Union’s Horizon 2020 research and innovation program under Marie Sklodowska-Curie Grant Agreement No. 722380 (the project SUPUVIR), the Center for Nanostructured Graphene sponsored by the Danish National Research Foundation (Project No. DNRF103), and VIL-LUM FONDEN (Grant No. 16498). N.S. acknowledges support from VILLUM FONDEN (Grant No. 00028233) and from the Independent Research Fund Denmark—Natural Sciences (Project No. 0135-004038). The authors declare no conflicts of interest.
© 2021 Author(s).