Polarization gating has been widely used to selectively probe the structure of superficial (<1mm) tissue. One of the most vivid applications is the diagnosis of early carcinomas and precancerous (dysplastic) lesions that originate in the mucosae of various organs such as the lung, breast, prostate, colon, etc. This diagnosis requires depth-selective tissue interrogation and polarization gating has the potential to provide that. However, the penetration depth selectivity of polarization gating has not been well understood. The knowledge of the penetration depth profile would allow investigators to identify the origins of polarization-gated signals in tissue and associate those with specific tissue structures that can be assessed using polarization-gated measurement. We develop analytical models and use polarized light Monte Carlo simulations to understand propagation of polarized light in tissue.
