Supercontinuum (SC) light source is certainly one of the best option for ultra-high resolution optical coherence tomography (UHR-OCT). Over the last few years several demonstrations have been done for each commonly used wavelength range [1-2-3]. Nowadays, SC dedicated to UHR-OCT is a mature technology with turn-key commercially available system . The new challenge to answer for SC source is the cost reduction one.
In this study, we demonstrate that a Q-switched based SC (QS-SC) could be an alternative to the current state of the art SC based on a Mode-Locked laser (ML-SC). This QS-SC, whose cost is less than 15 % of the ML-SC, offers similar possibilities in terms of bandwidth, beam quality and optical density within the OCT band . We demonstrate the usefulness of such a source by direct comparison with the ML-SC source commonly used. Our study includes a comparison of the pulse to pulse stability of both sources over the OCT wavelength range, where it is shown that the QS-SC is much more stable than the ML-SC. Also, a noise analysis conducted from the OCT point of view shows that the source repetition rate is a key parameter for any SC based OCT system. A comparison of images acquired from biological and non-biological samples is performed with emphasis on their contrast. Our conclusion is that a QS-SC can be used a useful source for UHR-OCT if compromise can be done in terms of speed of the detection unit. Finally, our study has been done at a central wavelength of 1270 nm, however the ultra-broad flat spectrum of the QS-SC makes it an interesting source for the 800 nm or visible range OCT too, opening the door for low-cost multi-band or multi-modal OCT.
1. K. Bizheva, B. Tan, B. MacLelan, O. Kralj, M. Hajialamdari, D. Hileeto, and L. Sorbara, “Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas,” Biomed. Opt. Express 8, 800-812 (2017).
2. W. Yuan, J. Mavadia-Shukla, J. Xi, W. Liang, X. Yu, S. Yu, and X. Li, "Optimal operational conditions for supercontinuum-based ultrahigh-resolution endoscopic OCT imaging," Opt. Lett. 41, 250-253 (2016).
3. C. Cheung, J. Daniel, M. Tokurakawa, W. Clarkson, and H. Liang, "High resolution Fourier domain optical coherence tomography in the 2 μm wavelength range using a broadband supercontinuum source," Opt. Express 23, 1992-2001 (2015).
Supercontinuum (SC) light is a well-established technology, which finds applications in several domains ranging from chemistry to material science and imaging systems [1-2]. More specifically, its ultra-wide optical bandwidth and high average power make it an ideal tool for Optical Coherence Tomography (OCT). Over the last 5 years, numerous examples have demonstrated its high potential [3-4] in this context. However, SC light sources present pulse-to-pulse intensity variation that can limit the performance of any OCT system  by degrading their signal to noise ratio (SNR). To this goal, we have studied and compared the noise of several SC light sources and evaluated how their noise properties affect the performance of Ultra-High Resolution OCT (UHR-OCT) at 1300 nm. We have measured several SC light sources with different parameters (pulse length, energy, seed repetition rate, etc.).
We illustrate the different noise measurements and their impact on a state of the art UHR-OCT system producing images of skin. The sensitivity of the system was higher than 95 dB, with an axial resolution below 4μm.
In this report we applied the principle of Master-Slave Interferometry (MSI) to an Optical Coherence Tomography (OCT)
employing a Super-Continuum (SC) light source. A-scans and B-scan images of biological and non-biological sample are
presented in order to demonstrate similar performance with the images obtained with the resampled Fourier Transform
(FT) based OCT technique. Dispersion tolerance of MSI method is demonstrated as a constant axial resolution over the
depth range even though dispersion is left uncompenstaed in the system.
We demonstrate that the recently proposed master-slave interferometry method is able to provide true dispersion free depth profiles in a spectrometer-based set-up that can be used for accurate displacement measurements in sensing and optical coherence tomography. The proposed technique is based on correlating the channelled spectra produced by the linear camera in the spectrometer with previously recorded masks. As such technique is not based on Fourier transformations (FT), it does not require any resampling of data and is immune to any amounts of dispersion left unbalanced in the system. In order to prove the tolerance of technique to dispersion, different lengths of optical fiber are used in the interferometer to introduce dispersion and it is demonstrated that neither the sensitivity profile versus optical path difference (OPD) nor the depth resolution are affected. In opposition, it is shown that the classical FT based methods using calibrated data provide less accurate optical path length measurements and exhibit a quicker decays of sensitivity with OPD.