Absolute distance measurement with heterodyne optical feedback on a Yb:Er glass laser

Absolute distance measurement based on optical feedback using a single-frequency Yb:Er glass laser is demonstrated via the combination of heterodyne detection and frequency sweep. The technique allows for the enhancement of the sensitivity of the laser response to self-mixing thanks to resonant excitation close to the relaxation-oscillation frequency peak. The experimental results on noncooperative targets are in good agreement with the theory, and the shape of the resulting signal is analyzed in both the temporal and the frequency domains considering the specific dynamic of the class B solid-state laser. Suggestions are provided for further improvements on the signal processing.