Using a Nd:YVO 4 microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal to noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity while in the autodyne configuration, the wave beating takes place inside the laser cavity and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performances than heterodyne interferometry for a wide range of laser power and detection level of noise. The experimental results are in good agreement with the theoretical predictions.

International audienceWeprovideatheoreticalstudyoffrequency-shiftedfeedback(FSF)lasers,i.e.,laserswithaninternalfrequency shifter,seededwithamonochromaticwave.Theresultingspectrumconsistsinasetofequidistantmodes,labeled by n, whose phases vary quadratically with n. We prove the emergence of a temporal fractional Talbot effect, leading to generation of Fourier-transform-limited pulses at a repetition rate tunable by the parameters of the FSF cavity (cavity length and frequency shift per round trip), and limited by the spectral bandwidth of the laser. We characterize in detail the output field of this so-called “Talbot laser” and emphasize its specific intensity fluctuations.WeevidenceconnectionswithsomeaspectsofnumbertheorybytheappearanceofGausssumsand thetaseriesintheexpressionofthelaserfield.Ourpredictionsareinfullagreementwiththeexperimentalresults published in Guillet de Chatellus et al. [Opt. Express 21, 15065 (2013)]. Practical applications and limitations are discussed