Subwavelength Raman spectroscopy

Near-field Raman spectroscopy has been performed on liquid CCl4. The spectrum, obtained through an aperture significantly smaller (λ/10) than the exciting wavelength (514.5 nm) with a good signal-to-noise ratio, presents polarization effects that are different from the far-field spectrum. The tip is shown to be polarized at 99.9% by the Raman near field. If the probe is modeled as a single dielectric sphere, the estimated Raman near-field amplitude amounts to about 103 V m−1. The frustration of the Raman near field by the probe allows to record the Raman spectrum of only 0.4 attomol, or 240 000 mol.