Measurement of linewidth and noise dependence on the optical feedback parameter C by means of an FM-Converted Self-Mix interferometer

Using a frequency-converted self-mix interferometer, we analyze with a new comprehensive approach, and then confirm with measurement results, the dependence of Schawlow-Townes (S-T) linewidth, frequency uncertainty linewidth and frequency noise spectral density from the optical feedback (or Acket's) parameter C. Theoretically, the S-T linewidth and the noise spectral density are both dependent on (1 + C)-2, whereas the frequency uncertainty varies as (1 + C)-1. We test these dependences with new original measurements, taken on two laser diodes with different emission wavelengths and linewidth and find excellent agreement with the theory.