Semi-analytical full-wave model for simulations of scans in optical coherence tomography with accounting for beam focusing and the motion of scatterers

A full-wave model for simulating images in spectral-domain optical coherence tomography (OCT) with rigorous accounting for the beam-focusing effects is developed. Due to the analytical description of beam focusing, the model is computationally rather efficient. It also uses a rigorous numerical summation of the contributions of the localized sub-resolution scatterers, accounting for variations in the phase-amplitude parameters of the incident and backscattered optical waves, with a subsequent integration of the latter over the objective aperture. In the limit of a weakly focused beam, the developed model has allowed for the validatation of the earlier proposed simplified model with a constant-radius beam. It is shown that, for weakly focused beams, utilization of the computationally more efficient simplified model is quite sufficient, especially when simulation of numerous OCT scans in tissues with moving scatterers is necessary. The relevant examples related to the OCT imaging of spatially inhomogeneous strains are given. When the application of strongly focused beams is indispensable to obtain ultimately high resolution in OCT scans, the developed rigorous model for strongly focused beams offers convenient possibilities for developing methods of numerical refocusing. Possibilities to ensure uniform, close-to-maximal resolution not only in the focus waist, but over the entire imaged depth range, are demonstrated in simulations based on the developed model. (letter)