The first OCT instruments scanned a reference mirror to sequentially acquire measurements across depth. This approach established the potential of coherence-gated, label-free imaging of biological samples. But it was fundamentally slow. Imaging speeds were limited to a few thousand depth scans per second. The development of Fourier-domain OCT parallelized signal capture across depth; in the time required to make a a single depth measurement using the older approach, a FD instrument could capture more than one thousand depth locations. This graduated OCT from cross-sectional imaging to wide-field, volumetric imaging and opened a broad set of new opportunities in clinical and biomedical applications.
In the decade following the invention of FD-OCT, technological research focused on the optical and photonic advances needed to realize higher-speed FD-OCT. With these efforts, OCT imaging speeds have surpassed 1 million depth scans per second, revealing a new barrier to imaging speed – data capture. In short, these systems generate data at a higher rate than electronics can capture, transfer, and/or process.
Circular-ranging is a variant of OCT that was developed to overcome this data capture limit. In CR, optical frequency comb sources are used to combine a set of equally spaced depth locations into a single measurement. When imaging over large depth ranges, this can reduce the required detection and data capture bandwidths by more than an order of magnitude. Our center has pioneered the CR approach and is continuing to develop the frequency comb sources, interferometer architectures, and signal processing algorithms that enable it [1-9]. We are working with our collaborators to translate the technology for both diagnostic and intraoperative imaging applications, with an early focus in the later on enhancing nerve visualization.
- Ben Vakoc
- Norman Lippok
- Stephanie Nam
- M. Siddiqui, A. S. Nam, S. Tozburun, N. Lippok, C. Blatter, and B. J. Vakoc, “High-speed optical coherence tomography by circular interferometric ranging,” Nat. Photonics, vol. 12, no. 2, pp. 111–116, Feb. 2018, doi: 10.1038/s41566-017-0088-x.
- T. S. Kim and B. J. Vakoc, “Stepped frequency comb generation based on electro-optic phase-code mode-locking for moderate-speed circular-ranging OCT,” Biomed. Opt. Express, vol. 11, no. 7, p. 3534, Jul. 2020, doi: 10.1364/BOE.392359.
- N. Lippok, B. E. Bouma, and B. J. Vakoc, “Stable multi-megahertz circular-ranging optical coherence tomography at 1.3 µm,” Biomed. Opt. Express, vol. 11, no. 1, p. 174, Jan. 2020, doi: 10.1364/BOE.11.000174.
- N. Lippok and B. J. Vakoc, “Resolving absolute depth in circular-ranging optical coherence tomography by using a degenerate frequency comb,” Opt. Lett., vol. 45, no. 5, p. 1079, Mar. 2020, doi: 10.1364/OL.389085.
- N. Lippok, M. Siddiqui, B. J. Vakoc, and B. E. Bouma, “Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging,” Phys. Rev. Appl., vol. 11, no. 1, p. 014018, Jan. 2019, doi: 10.1103/PhysRevApplied.11.014018.
- R. Khazaeinezhad, M. Siddiqui, and B. J. Vakoc, “16 MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating,” Opt. Lett., vol. 42, no. 10, p. 2046, May 2017, doi: 10.1364/OL.42.002046.
- S. Tozburun, M. Siddiqui, and B. J. Vakoc, “A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography,” Opt. Express, vol. 22, no. 3, p. 3414, Feb. 2014, doi: 10.1364/OE.22.003414.
- M. Siddiqui and B. J. Vakoc, “Optical-domain subsampling for data efficient depth ranging in Fourier-domain optical coherence tomography,” Opt. Express, vol. 20, no. 16, p. 17938, Jul. 2012, doi: 10.1364/OE.20.017938.
- M. Siddiqui, S. Tozburun, E. Z. Zhang, and B. J. Vakoc, “Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation,” Opt. Express, vol. 23, no. 5, p. 5508, Mar. 2015, doi: 10.1364/OE.23.005508.