Absolute linear-in-k spectrometer designs enabled by freeform optics

Linear-in-wavenumber, k , spectrometers have the merits of saving signal processing time and improving the sensitivity of spectral-domain optical coherence tomography (SD-OCT) by avoiding post- k -interpolation. We report on an approach leveraging freeform optics to linearize spectrometers in k to achieve an extremely low residual k -nonlinearity in design. A freeform lens reduced the k -nonlinearity from 2.47% for a benchmark spectrometer to 2.79 × 10 −5 % and 3.36 × 10 −9 % using the Fringe Zernike coefficients up to the 16 th term and 37 th term, respectively. A simulation model was developed to evaluate the performance of SD-OCT ...
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