Optical coherence tomography using a photorefractive polymer composite

We report on the possibility of using a photorefractive polymer composite device as a coherence gate for optical coherence tomography. Such a system could enable high-resolution 3-dimensional images of tissue samples to be holographically stored, and read out in real-time, or at a subsequent time. A free space system based on the Michelson interferometer is used to illuminate a photorefractive polymer device with two coherent beams. Interference of these beams results in an intensity distribution, which is consequently stored as a refractive index hologram inside the polymer. The image-carrying object beam is then reproduced from the first order diffraction of a probe beam through the device, and is captured on a CCD camera. Devices used are based on a poly(N-vinylcarbazole) (PVK):2,4,7-trinitro-9-fluorenone dimalenitrile (TNFDM) charge transport network with the electro-optic organic chromophore 1-(2'-ethylhexyloxy)-2,5-dimethyl-4-(4"-nitrophenylazo)benzene (EHDNPB). Using a 1% concentration of TNFDM, whole-field 2-dimensional image planes are successfully recorded in a few seconds with a 7mW HeNe laser at 633nm. Readout of the hologram is also performed using the same source.