Surface Phonon Coupling within Boron Nitride Nanotubes Resolved by a Novel Near-Field Infrared Pump-Probe Imaging Technique
نویسندگان
چکیده
Surface phonon-polariton (SPhP) modes exist under optical excitation of polar materials, and are accessible using scattering type near-field optical microscopy (s-SNOM). Hexagonal boron nitride (hBN) and boron nitride nanotubes (BNNTs) can exhibit such modes under IR excitation, in spectral regions where the permittivity is negative. Herein we present pump-probe continuous wave (CW) sSNOM a novel two color pump-probe infrared technique that uses two cw tunable light sources and is based on s-SNOM, see Figure 1. [1] The technique for the first time enables the nanometer spatial resolution of couplings between surface phonons longitudinal optical and surface phonon polaritons.
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