An electric field enhanced by a metallic nanoprobe has locally induced coherent anti-Stokes Raman scattering (CARS) of adenine molecules in a nanometric DNA network structure. Owing to the third-order nonlinearity, the excitation of the CARS polarization is extremely confined to the end of the tip apex, resulting in a spatial resolution far beyond the diffraction limit of light. Our tip-enhanced CARS microscope visualized the DNA network structure at a specific vibrational frequency ($\sim 1337\mathrm{c}{\mathrm{m}}^{\mathrm{-}\mathrm{1}}$) corresponding to the ring-breathing mode of diazole of adenine molecules.

We have developed a new coherent anti-Stokes Raman scattering (CARS) microscopy system with a collinear configuration for use in the fingerprint region. The system consists of a picosecond laser system and a transmission-type laser scanning microscope without a pinhole in front of the detector. The observable Raman-shift region is $900–1750 {\mathrm{cm}}^{-1}$, the spectral resolution is $30 {\mathrm{cm}}^{-1}$, and the spatial resolution is smaller than $1 \mathit{\mu }\mathrm{m}$ in the lateral direction and $3.2 \mathit{\mu }\mathrm{m}$ in the depth direction, with objectives with a numerical aperture of 0.65. CARS spectra and images of polystyrene beads are demonstrated, and CARS imaging of a viable yeast cell is attempted.

On the basis of the mechanism of surface enhanced Raman scattering, it is shown that coherent anti-Stokes Raman scattering (CARS) of molecules attached to isolated gold nanoparticles are strongly enhanced and the signal from each particle is well localized. In addition to well-known advantages of CARS, the surface enhanced CARS combined with a scanning system of metallic nanoprobe tip can realize high spatial resolution CARS microscopy beyond the diffraction limit of light by locally enhancing the weak signals from the small sample volume. This concept is realized by tip-enhanced coherent anti-Stokes Raman spectroscopy using a metallic nanoprobe of near-field scanning optical microscope.

A compact Fourier-transform IR spectrometer without a moving mechanism was developed. The spectrometer consists of a shearing interferometer for forming a spatially distributed interferogram and an IR array detector for observing the interferogram. The shearing interferometer of the developed system is a birefringent interferometer with a Savert plate; the IR array detector is a PtSi Schottky- barrier detector with 4096 elements. The optics and the system configuration are described in detail, and the experimental results of the IR absorption spectra of polystyrene and polyethylene terephthalate film are shown. The developed optics is as small as 20 × 6 cm ϕ in size. The spectral resolution of the prototype system is ~ 27.6 cm⁻¹ between 5000 and 2000 cm⁻¹. The methods and their possibilities of resolution improvement are also described.