Infrared laser microscopy of living cells using a CW optoparametric oscillator as radiation source

We have developed a new method to image microscopic structures in living cells using as bright IR radiation source: our high power CW optoparametric oscillator (OPO) with up to 2.7 W output power and a near infrared laser. We present the first results for the chemical microscopy of hepatocytes (liver cells) using a frequency of 2920 cm^-1 coinciding with the absorption band of lipids and at 1.5 μm corresponding to the overtones of water. Infrared microscopy allows studying processes of living cells in cases where fluorescence markers are cell damaging, alter the natural function of a protein in a cell or where labeling is impossible. In the infrared spectral range, accessible to our laser systems, substances can be identified according to their specific absorption in the so-called fingerprint region. Moreover, the absorption is directly proportional to the number of molecules, which makes it the appropriate method for quantitative measurements. Our method opens the possibility to investigate rapid changes of chemical behavior and the dynamics of small bio-molecules in living cells. In addition, we demonstrate by using near-field microscopy a spatial resolution of less than 30 nm (≪λ/100) at λ=3222 nm (3104 cm^-1).