In vivo human retinal swept source optical coherence tomography and angiography at 830\xa0nm with a CMOS compatible photonic integrated circuit

Elisabet A Rank,Rainer A Leitgeb,Rainer Hainberger,Paul Muellner,Stefan Gloor,Matthias Salas,Marcus Duelk,Wolfgang Drexler,Stefan Nevlacsil,Martin Sagmeister,Jochen Kraft

doi:10.1038/s41598-021-00637-4

Abstract

Photonic integrated circuits (PIC) provide promising functionalities to significantly reduce the size and costs of optical coherence tomography (OCT) systems. This paper presents an imaging platform operating at a center wavelength of 830 nm for ophthalmic application using PIC-based swept source OCT. An on-chip Mach–Zehnder interferometer (MZI) configuration, which comprises an input power splitter, polarization beam splitters in the sample and the reference arm, and a 50/50 coupler for signal interference represents the core element of the system with a footprint of only (12 times 5);{text {mm}}^2. The system achieves 94 dB imaging sensitivity with 750 upmu W on the sample, 50 kHz imaging speed and 5.5 upmu m axial resolution (in soft tissue). With this setup, in vivo human retinal imaging of healthy subjects was performed producing B-scans, three-dimensional renderings as well as OCT angiography. These promising results are significant prerequisites for further integration of optical and electronic building blocks on a single swept source-OCT PIC.

Highlights

Photonic integrated circuits (PIC) provide promising functionalities to significantly reduce the size and costs of optical coherence tomography (OCT) systems
In a recent study we showed, to the best of our knowledge, the first in vivo human retinal tomograms using two designs of PIC based arrayed waveguide gratings (AWG) for spectral domain OCT (SD-OCT), in which the above-mentioned parameters were of critical importance as well[15]
Back-reflected light from the free-space sample and reference arms is interferred in the on-chip 50/50 coupler, exits the PIC at the end facet and is acquired in free-space using a customized dual balanced receiver

Summary

Introduction

Photonic integrated circuits (PIC) provide promising functionalities to significantly reduce the size and costs of optical coherence tomography (OCT) systems. The system achieves 94 dB imaging sensitivity with 750 μ W on the sample, 50 kHz imaging speed and 5.5 μ m axial resolution (in soft tissue) With this setup, in vivo human retinal imaging of healthy subjects was performed producing B-scans, three-dimensional renderings as well as OCT angiography. Germanium photodiodes with a 20 GHz bandwidth were integrated as well With these systems, sensitivities of 64 dB and 53 dB were achieved for OCText and OCTint, respectively, and B-scans of Scotch tape as well as enface images of pumice and a decayed leaf were shown. Van Leeuwen et al reported an MZI with an on-chip reference arm for 1550 nm[12] They achieved a system sensitivity of 83 dB and an axial resolution of 15.2 μ m. To the best of our knowledge, all reported on-chip interferometers for SS-OCT application are in the telecom wavelength region (1300–1550 nm), which are not ideal for human retinal imaging due to increased water absorption of ocular media in these wavelength ranges

Methods

Results

Conclusion