FM Self-mixing Interferometer Measurement Performance

Self-mixing interferometry achieves remarkable performance thanks to the frequency modulation reading. In this case the noise floor is no longer due to shot noise, as for amplitude modulation, but to the laser's frequency noise. This work experimentally compares the noise floor of this particular kind of interferometer for different laser types, DFB and VCSEL, which exhibit different line broadenings. Experimental measurement of the FM noise spectrum confirms the theoretical treatment that it is determined by the laser's linewidth. In the particular case of a VCSEL laser, the 1/f noise in frequency modulation clearly indicate a gaussian broadening of the laser linewidth.