All-depth dispersion cancellation in spectral domain optical coherence tomography using numerical intensity correlations

Ole Bang,Mikkel Jensen,Michael Maria,Thomas Feuchter,Adrian Podoleanu,Niels Møller Israelsen

doi:10.1038/s41598-018-27388-z

Ole Bang, Mikkel Jensen + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-27388-z

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Abstract

In ultra-high resolution (UHR-) optical coherence tomography (OCT) group velocity dispersion (GVD) must be corrected for in order to approach the theoretical resolution limit. One approach promises not only compensation, but complete annihilation of even order dispersion effects, and that at all sample depths. This approach has hitherto been demonstrated with an experimentally demanding ‘balanced detection’ configuration based on using two detectors. We demonstrate intensity correlation (IC) OCT using a conventional spectral domain (SD) UHR-OCT system with a single detector. IC-SD-OCT configurations exhibit cross term ghost images and a reduced axial range, half of that of conventional SD-OCT. We demonstrate that both shortcomings can be removed by applying a generic artefact reduction algorithm and using analytic interferograms. We show the superiority of IC-SD-OCT compared to conventional SD-OCT by showing how IC-SD-OCT is able to image spatial structures behind a strongly dispersive silicon wafer. Finally, we question the resolution enhancement of sqrt{2} that IC-SD-OCT is often believed to have compared to SD-OCT. We show that this is simply the effect of squaring the reflectivity profile as a natural result of processing the product of two intensity spectra instead of a single spectrum.

Highlights

We show the superiority of intensity correlation (IC)-spectral domain (SD)-optical coherence tomography (OCT) compared to conventional spectral domain OCT (SD-OCT) by showing how IC-SD-OCT is able to image spatial structures behind a strongly dispersive silicon wafer
L is the physical axial position relative to the surface of the sample, in this case 255 microns. β2 = ∂2β/∂ω2 is the group velocity dispersion (GVD) parameter, c is the speed of light in vacuum, and Δλ and λc are the full-width at half maximum (FWHM) and centre wavelength, respectively
We show that we numerically can eliminate the GVD due to the sample, irrespective of the scattering depth, allowing us to maintain the theoretical axial resolution at all depths, and this using a conventional SD-OCT set-up with only a single spectrometer

Summary

Introduction

All reports so far on implementing IC-SD-OCT, both numerical and hardware-wise, share two major drawbacks compared to conventional SD-OCT: (1) Halving of the imaging depth, and (2) the appearance of IC artefacts stemming from intensity cross terms. Extending the numerical scheme of Shirai et al.[28], we here for the first time demonstrate ultra-high resolution SD-OCT with all-depth multi-interface sample dispersion removal with significant artefact reduction and full imaging depth using a conventional SD-OCT setup.

Results

Conclusion