Title: Elucidating the Photon Migration Effects in Incubated Chicken Eggs using Time-Domain Diffuse Optics 
Speaker: Lennard van den Tweel (Wageningen University and Research) 
Date: Wednesday, 20 May 2026, 16:00 Central European Summer Time (CEST)

The early and non-invasive assessment of chicken embryonic sex and viability is of great interest. This interest is driven by the ethical dilemma surrounding the culling of non-productive day-old male chicks in layer-hen production and by the need to improve hatchery efficiency. Optical techniques are widely investigated for these applications, but are challenged by the complex optical properties and heterogeneous structure of avian eggs. Here, we show that chicken eggs display unusual photon trapping behavior due to the eggshell behaving like an integrating sphere, considerably extending photon time-of-flight. Time-domain diffuse optical spectroscopy (TD-DOS) on egg phantoms, supported by Monte Carlo simulations and post-dispersive filtering experiments, rule out fluorescence as the source for the long photon time-of-flight. These results point to diffuse reflections at the inner surface of the eggshell as the source of the long photon time-of-flight. Despite these boundary effects, the retrieval of internal bulk optical properties remains feasible via inversion of the diffusion approximation after selection of appropriate boundary conditions, as was demonstrated in incubated eggs. Finally, phantom experiments illustrate how the integrating sphere affects the temporal response of time-resolved Raman and fluorescence measurements, highlighting critical challenges in non-invasive optical characterization of avian embryos.