Output characterization of a frequency shifted feedback laser: theory and experiment

Frequency shifted feedback cavity (FSFC) lasers can generate continuous broadband radiation or periodic picosecond pulses. To better understand these two different regimes a passive FSFC is modeled and its output in the time and frequency domains is calculated. Calculations of the FSFC output indicate that peaks observed using a Fabry-Perot spectrum analyzer can only occur when the FSFC cavity length and intracavity frequency shift satisfy a resonance condition. Calculations also indicate that a radio frequency spectrum analysis of the intensity should show sharp peaks which are independent of the FSFC frequency shift. Additionally, pulses propagating in a FSFC are insensitive to frequency shift detunings, suggesting applications as a stable source of ultrashort laser pulses. Experimental evidence confirming these findings is reported. Results indicate that a FSFC does not support conventional laser modes