We describe a swept source based phase sensitive optical coherence microscopy (OCM) system for photothermal imaging of gold nanorods (GNR). The phase sensitive OCM system employed in the study has a displacement sensitivity of 0.17 nm to vibrations at single frequencies below 250 Hz. We demonstrate the generation of phase maps and confocal phase images. By displaying the difference between successive confocal phase images, we perform the confocal photothermal imaging of accumulated GNRs behind a glass coverslip and behind the scattering media separately. Compared with two-photon luminescence (TPL) detection techniques reported in literature, the technique in this study has the advantage of a simplified experimental setup and provides a more efficient method for imaging the aggregation of GNR. However, the repeatability performance of this technique suffers due to jitter noise from the swept laser source.
Spectrometer based and swept source based phase sensitive Fourier Domain OCT systems are compared in terms of the stability of the retrieved signal phase. The spectrometer based system performs with a significantly better phase stability with less uncertainty in the output, whereas the output of the swept source based system is influenced by the jitter noise that creates jumps to the retrieved phase. The experimentally obtained phase traces from the spectrometer based system match well to relevant mathematics.