Low-frequency multiplex CARS microscopy with a high-repetition near-infrared supercontinuum laser

We have developed a multiplex coherent anti-Stokes Raman scattering microscope effective for low-wavenumber measurement by combining a high-repetition supercontinuum light source of 1064 nm and a near-infrared high-sensitivity InGaAs diode array. This system could observe the low-wavenumber region down to 55 cm(-1) with high sensitivity. In addition, using spectrum shaping and spectrum modulation techniques, we simultaneously realized a wide bandwidth (<1800 cm(-1)), high wavenumber resolution (9 cm(-1)), high efficiency, and increasing signal-to-noise ratio by reducing the effect of the background shape in the low-wavenumber region. Spatial variation of a sulfur crystal phase transition with metastable states was visualized.