Optical inspection and thickness measurement of nanostructures with optical coherence tomography based on single channel acquisition

In this study, a phase-sensitive, swept-source optical coherence tomography (SS-OCT) system is implemented for the optical measurement of nanostructures. A new approach is proposed to reduce the phase errors, resulting from trigger jitter of the swept source and the asynchronization between the A-scan trigger and OCT signal at the data acquisition end, with a narrowband fiber Bragg grating to generate the accurate A-scan trigger. Furthermore, combining the common-path configuration with the proposed approach, the displacement sensitivity can be calculated to be 80 pm when the swept source is operated at 30 kHz. Finally, the conducting glass was scanned with the proposed approach to quantitatively measure the thickness of conducting layer. The results show that the proposed SS-OCT approach can make be a potentially useful tool for noninvasive, real-time inspection of nanostructures.