  Optical diffraction tomography (ODT) is a powerful non-invasive 3D imaging
technique, but its combination with broadband light sources is difficult. In
this study, we introduce ultrabroadband ODT, covering over 150 nm of visible
spectral bandwidth with a lateral spatial resolution of 150 nm. Our work
addresses a critical experimental gap by enabling the measurement of broadband
refractive index changes in 3D samples, a crucial information that is difficult
to assess with existing methodologies. We present broadband, spectrally
resolved ODT images of HeLa cells, obtained via pulse-shaping based Fourier
transform spectroscopy. The spectral observations enabled by ultrabroadband
ODT, combined with material-dependent refractive index responses, allow for
precise three-dimensional identification of the nanoparticles within cellular
structures. Our work represents a crucial step towards time and
spectrally-resolved tomography of complex 3D structures with implications for
life and materials science applications.
