What does brain cancer surgery and the search for extra-terrestrial life have in common? They are both limited by the very same challenge: characterising the nature and probing the structure of living tissues. For many tumour types, visual differentiation of tumours, infiltration zones and healthy tissues is difficult during surgery, if not impossible due to the lack of obvious visual differences. This limitation translates into an incomplete surgical resection, leaving residual tumour tissue and increasing the likelihood of resurgence. The search for living organisms beyond the Earth essentially relies on the detection of atmospheric biomarkers, such as oxygen, methane and ozone that are produced by biotic activity. However, these compounds can also be produced abiotically, complicating the unequivocal attribution to living processes. Identifying more robust biomarkers, with near-zero false-positive scenarios is thus paramount.
Most optical applications in medicine and astrophysics only leverage the intensity and wavelength of a wave of light. However, its polarisation state (spatial orientation of the wave’s electrical field) is seldom used. A key characteristic of the polarisation state of a wave of light is to carry information about its interaction with matter, whether it is aerosols, living tissues or any other medium. In this talk, I will detail how accurately measuring polarisation induced by the interaction of a wave of light with matter provides a remote, non-invasive means to investigate the spatial structure of a material of interest. Besides astrophysics and medicine, other applications include geology, climate, food and agriculture research. Light polarisation is ubiquitous in nature and so fundamental that applications are endless.
