New dual-comb functional near infrared spectroscopy (fNIRS) technique: study of optical properties and perturbation localization

We present a new functional near infrared spectroscopy (fNIRs) technique based on dual-comb optical interrogation applied to dispersive media (DC-fNIRS) that can retrieve the frequency response of a living tissue (such as the brain) by parallel sampling of its frequency response in amplitude and phase at specific frequencies. With this information, we can retrieve the impulse response (diffuse-time-of-flight measurements, DTOF) of the medium and extract the absolute optical properties of the tissue and the spatial localization of perturbations for functional analysis with millisecond temporal resolution and noiseless optical gain, increasing the penetration. We have tested these predictions studying a biomimetic phantom with the same optical characteristics as brain tissue confirming the capacities of the DC-fNIRs technique for diffuse media. The system is patent pending PCT/ES2022/070176.