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

We have developed a multiplex Coherent anti-Stokes Raman scattering (CARS) microscope effective for low-wavenumber measurement by combining a high-repetition supercontinuum light source of 1064 nm and an 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 low-wavenumber region. Spatial variation of a sulfur crystal phase transition with metastable states was visualized.