Combined OCT and CARS using a single ultrashort pulse Ti:Sapphire laser

Optical coherence tomography (OCT) is a non-invasive in vivo biomedical imaging modality capable of three-dimensional visualization of tissue morphology permitting imaging at high speed and sensitivity. Coherent Anti- Stokes Raman Scattering (CARS) is a nonlinear spectroscopic technique which provides molecular information due to a four wave mixing process. In order to extend the performance of OCT towards detecting the molecular fingerprint of biological samples a combined CARS/OCT setup has been developed that employs only a single ultrashort pulse Ti:Sapphire laser which enables high axial resolution OCT and simultaneously combined with a spectral shaper a CARS setup. During first measurements the same area of a sample was imaged twice, applying OCT and CARS consecutively. OCT was used to perform three-dimensional morphological screening. Due to CARS additional chemical information could be gained for two dimensions. The spectrum was modified computer controlled to match the requirements for the generation of a CARS signal whereas for OCT the unmodified spectrum was applied. Fluids such as dimethylsulfoxide (DMSO) and PBS were compared in a cuvette to demonstrate the functionality of the multimodal setup. As a biological sample a 100 m thickcr oss section through a human optic nerve surrounded by sclera was investigated.