TY - JOUR AU - Hu, Chenfei AU - Field, Jeffrey J. AU - Kelkar, Varun AU - Chiang, Benny AU - Wernsing, Keith AU - Toussaint, Kimani C. AU - Bartels, Randy A. AU - Popescu, Gabriel PY - 2020 DA - 2020/06/01 TI - Harmonic optical tomography of nonlinear structures JO - Nature Photonics AB - Second-harmonic generation microscopy is a valuable label-free modality for imaging non-centrosymmetric structures and has important biomedical applications from live-cell imaging to cancer diagnosis. Conventional second-harmonic generation microscopy measures intensity signals that originate from tightly focused laser beams, preventing researchers from solving the scattering inverse problem for second-order nonlinear materials. Here, we present harmonic optical tomography (HOT) as a novel modality for imaging microscopic, nonlinear and inhomogeneous objects. The HOT principle of operation relies on interferometrically measuring the complex harmonic field and using a scattering inverse model to reconstruct the three-dimensional distribution of harmonophores. HOT enables strong axial sectioning via the momentum conservation of spatially and temporally broadband fields. We illustrate the HOT operation with experiments and reconstructions on a beta-barium borate crystal and various biological specimens. Although our results involve second-order nonlinear materials, we show that this approach applies to any coherent nonlinear process. SN - 1749-4893 UR - https://doi.org/10.1038/s41566-020-0638-5 DO - 10.1038/s41566-020-0638-5 ID - Hu2020 ER -