Suppression of FM-to-AM conversion in phase modulated third-harmonic generation process

Abstract Phase modulation to amplitude modulation (FM-to-AM) conversion occurring in phase modulated third-harmonic generation (THG, process 1 ω  + 2 ω  → 3 ω ) process is investigated. To suppress the FM-to-AM conversion, a group-velocity-matching relationship is derived, which appears to be dependent on the ratio of modulation depth of 2 ω –1 ω pulses. Numerical simulations indicate that the FM-to-AM conversion in phase-modulated THG process can be suppressed effectively by satisfying that group-velocity-matching relationship.