Electronic method for extracting the amplitude and phase of a signal in a synchronous detector and application thereof in interferometric circuits

An interferometer comprising:

• a light source;
• a signal arm optically coupled to the light source to receive light from the light source;
• a reference arm optically coupled to the light source to also receive the light from the light source;
• and
• a lock-in amplifier optically coupled via a detector to the signal arm and the reference arm to detect an electrical signal Idet, the electrical signal Idet containing a modulated part Imod of the form Imod∝ES*f(t)*cos(φS−φR(t)), where φR(t) and f(t) are two known temporal modulation functions and where Es and φS correspond to amplitude and phase signals, the lock-in amplifier being programmed to:
• multiply said electrical signal by two references signals C(t) and S(t) constructed from known temporal modulation functions φR(t) and f(t);
• integrate the two signals resulting from the two multiplications defined at the previous step during a time tint;
• and
• determine the amplitude and phase of said signal from the quantities X and Y resulting from the integrations defined at the previous step,
• wherein said electrical signal is multiplied by two references signals C(t) and S(t) that can be decomposed on the same set of frequencies as those present in Imod.