Advantages and limitations of all-fiber quasi-Bessel beam probes: theory and practice: 1085419

Non-Gaussian beams can provide extended depth of focus (DOF) at constant and potentially uncompromised transverse resolution, as well as a degree of self-reconstruction after beam shadowing, which may be present in tissue imaging. Hence such beams are being developed for imaging systems throughout many disciplines, including endoscopic imaging, where they hold great potential. General possibilities include up to more than 20-fold extension of DOF, tunable working distance, imaging around obstacles and integrated all-fiber designs. In all-fiber based optical imaging systems; however, these advantages are limited by system design considerations. Trade-offs between miniaturization, extended DOF, SNR, and fiber availability arise, and estimating the effects of design modifications can be difficult and time consuming. We model zero-order quasi-Bessel illumination and detection for a range of common probe and sample materials based on an analytic solution of the Fresnel diffraction integral and compare the results to Gaussian beams. We show that these beams, on scales that match optical fiber dimensions, generally have an upper limit for the spot size above which their distinct advantages over Gaussian beams fade. Similarly, we show the existence of a lower limit of practical performance of quasi-Bessel beams, where the imaging SNR penalty compared to a Gaussian beam becomes significant. Additionally to general theoretic considerations we discuss designs, modeling and characterization of all-fiber imaging probes. This work provides an accessible overview for researchers to estimate what potential benefit non-Gaussian beams can introduce into their optical imaging system.