Image sensor for spectral‐domain optical coherence tomography on a chip

Abstract

This Letter presents a global shutter image sensor based on PIN photodiodes intended to be used for optical coherence tomography (OCT) in the spectral domain, where the light is brought to the photodiodes via optical waveguides monolithically integrated on top of electronics in a photonic layer. Photodiodes are optimised to have the peak responsivity in the wavelength range between 800 and 900 nm, while the main features of electronics are high signal-to-noise ratio, high frame rate, low-power consumption and low noise. The sensor is designed using 0.35 µm high voltage CMOS and employing low doped epitaxial starting material in order to improve the detector efficiency by enabling fully depleted photodiodes and lowering the crosstalk. Image sensor parameters are obtained using the photon-transfer curve method and compared with commercial cameras for OCT.