Phase-Sensitive Optical Coherence Tomography for Dynamic Photothermal Detection And Imaging of Gold Nano-Rods in Scattering Media and Biological Tissue

Gold nanoparticles are particularly attractive agents in medical imaging and laser therapy due to their unique optical properties. This study seeks to propose and analyse solutions aimed at imaging the distribution of gold nanoparticles in scattering media and biological tissue using a photothermal modulation technique combined with phase sensitive Optical Coherence Tomography (OCT). In this thesis, a spectrometer based phase sensitive OCT system and a swept source based phase sensitive OCT system are developed separately to fulfil this goal. In each OCT system, a Ti:Sa laser beam is coaxially combined with the OCT probing beam. The photothermal detection of gold nano-rods in multiple layer of the sample is completed by fixing the combined beam on a single lateral position on the sample and modulating the frequency of the Ti:Sa beam to the sample. The photothermal imaging of gold nano-rods in multiple layers of the sample is achieved by raster scanning the combined beams over the sample, modulating the Ti:Sa beam to the sample and then generating high contrast en-face images displaying the phase values retrieved from the OCT signal.

Using the recently developed Complex Master/Slave interferometry technique, en-face images can be acquired in real time. In this thesis, application of this technique to a swept source based OCT system is presented. A system is specifically developed to produce en-face phase images of multiple layers of the studied sample. By doing this, the phase sensitive function of the Complex Master/Slave interferometry technique is demonstrated for the first time.