Integration on a microchip: A glimpse into the future of optical coherence tomography

Optical coherence tomography (OCT) is a noninvasive, three-dimensional imaging technique that offers close-to-histology-level image quality. Based on broadband spectral interferometry, OCT has enabled clinical applications ranging from ophthalmology to cardiology that revolutionized in vivo medical diagnostics. Considering the size and cost of a commercial OCT system, it is essential to investigate different approaches for realizing a compact and low-cost OCT system in order to make it accessible to a significantly larger group of applications and users. Exploiting integrated optics, several central components of an OCT system have been assembled on a microchip so far. Silicon based designs have the advantage of complementary metal-oxide-semiconductor (CMOS) compatible high-volume production while indium phosphate (InP) based designs have the possibility of monolithic integration of the light source and the detector with other components. In this chapter, the design considerations, theoretical analysis and experimental results of the passive integrated optical components of an on-chip OCT system including interferometer, spectrometer, reference arm, and sample arm will be presented. Active components (light source and detectors) are beyond the scope of this chapter.