Submicrometer axial resolution optical coherence tomography

Optical coherence tomography (OCT) with unprecedented submicrometer axial resolution achieved by use of a photonic crystal fiber in combination with a compact sub-10-fs Ti:sapphire laser (Femtolasers Produktions) is demonstrated for what the authors believe is the first time. The emission spectrum ranges from 550 to 950 nm $({\lambda }_c=725 \mathrm{nm}$, $P_{\mathrm{out}}=27 \mathrm{mW})$, resulting in a free-space axial OCT resolution of $\sim 0.75 \mathit{\mu }\mathrm{m}$, corresponding to $\sim 0.5 \mathit{\mu }\mathrm{m}$ in biological tissue. Submicrometer-resolution OCT is demonstrated in vitro on human colorectal adenocarcinoma cells HT-29. This novel light source has great potential for development of spectroscopic OCT because its spectrum covers the absorption bands of several biological chromophores.