High-speed 2D-scan for optical coherence tomography

To overcome the main limitations imposed by time-domain optical coherence tomography (TD-OCT) [1] and Fourierdomain (FD)-OCT [2], a novel approach based on analog optical signal processing has been successfully applied to detect a 2-interface target consisting of a 150 μm thick transparent polyvinyl chloride (PVC) layer. The implemented axial (A)-scan functionality exhibits a rate of 1 MHz, a depth of range of 3.2 mm, a sensitivity of dBm and a dynamic range exceeding 50 dB. The main critical issue of the present architecture, i.e. the uniformity of axial resolution along the range, has been discussed and a technical solution is identified. In addition, an optical beam forming/steering system based on a phased array of optical emitters for implementing the Β-scan functionality (with reference to intravascular OCT — IV-OCT [3]), is presented. The required integrated optical circuit for proper power splitting and phase control on each optical path has been successfully designed, fabricated and tested. It is based on grating couplers, multimode interference (MMI) splitters and thermal phase shifters, potentially leading to a Β-scan rate of 100's of KHz.