Optical Feedback Interferometry: from Basics to Applications of Laser Flowmetry
Optical feedback interferometry (OFI) is a contactless technique that is employed for measuring parameters related to object’s motion. The light emitted by a laser is backreflected or scattered from a moving object and a small portion of the scattered waves re-enters the laser cavity and impacts the laser's emission properties. We review the theoretical basics of optical feedback interferometry and explain the physical principles in the frame of laser Doppler flowmetry. We present a model derived from the Lang and Kobayashi rate equations to show the particular features of the optical feedback signal in temporal and frequency domain. In addition, we present experimental measurements relative to the detection of flowing particles in a microchannel, the measurement of unsteady flows and the quantification of blood perfusion in skin, which demonstrate the potential use of OFI sensors in the assessment of fluidic systems of interest in chemical and biomedical engineering.