Optical spectroscopy in the time-domain beyond 1.1 μm: A tool for the characterization of diffusive media

Summary form only given. Time-resolved diffuse optical spectroscopy (TRS) is a valuable technique for the characterization of a variety of diffusive media like biological tissues, fruit, wood and pharmaceutical tablets. The technique is based on the injection of a short pulse (~ps) on the surface of the sample. The time-of-flight distribution (TOF) of photons detected on a different location of the surface gives information about the absorption and scattering probabilities [1]. Due to the widespread application of the technique to biological tissues, where there is a low light attenuation in the 0.6-1.1 μm range, the range beyond 1.1 μm is relatively unexplored with time-resolved techniques, also because of the difficulty to combine mode-locked continuously tunable sources with detectors having a sensitivity down to the single-photon level. Nevertheless beyond 1.1 μm there are organic compounds that contribute to interesting spectral structures like collagen, lipids, hydroxyapatite, starch, glucose and lignin. In this work we explore the application of TRS beyond 1.1 μm to the characterization of a variety of samples.