Disclosed are improved optical detection systems and methods comprising interferometric detection systems, methods for determining a characteristic property of a fluid, methods for calculating a shift between at least two signals, computer program products encoded in a computer readable medium, and computational systems. Also disclosed are label-free, free-solution, and/or real-time measurements of characteristic properties and/or chemical events using the disclosed techniques. Also disclosed are various biosensor applications of the disclosed techniques. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.