Photodiode-free Doppler velocimeter based on self-mixing effect in commercial VCSELs

In this paper, we explore a new signal acquisition method for laser Doppler velocimeter based on the self-mixing technique. The self-mixing technique is applied on commercial multimode transverse Vertical-Cavity Surface-Emitting Lasers (VCSELs) and the signal is acquired by amplification of the junction voltage of the laser diode when it was usually picked-up with an external photodiode. The sensor developed exhibits up to 25dB signal-to-noise ratio for a wide velocity range. We present a study of the sensitivity of such photodiode-free sensors versus the laser static conditions and we compare the results with usual photodetected signals. Finally we expose the advantages of this technique and propose new applications for self-mixing sensors.