Laser Self-Mixing for Measurement of Higher Velocities

Laser self-mixing is usually used for measurement of low velocities and vibrations. In a paper just published in Optical Engineering the authors explore the use of the method for the measurement of velocity and density of gas jets based on self-contained optical feedback.

Self-mixing interferometry has previously been applied to flow-velocity measurements often aimed at biological applications, such as blood flow characterisation, Brownian motion and biological species dynamic studies. There has been high interest in this area resulting in a number of studies with measurements of relatively small velocity from 0.1 mm/s to 10 cm/s with high accuracy.

This new study successfully demonstrates how higher velocities can be measured and shows the impact of different target geometries and characteristics on the quality of the detected signal. The authors use this as a basis to assess the potential for future gas-jet characterisation applications which would be an entirely new application for this technique. A detailed investigation into different targets is presented covering velocity measurements of solid targets of up to 50 m/s and flow velocities of up to 1 m/s - significantly higher than any previously published measurement.