Tunable, Stable Source of Femtosecond Pulses Near 2 {\mu}m via Supercontinuum of an Erbium Mode-Locked Laser

摘要

A source of ultrashort pulses of light in the 2 {\mu}m region was constructedusing supercontinuum broadening from an erbium mode-locked laser. The outputspectrum spanned 1000 nm to 2200 nm with an average power of 250 mW. A pulsewidth of 39 fs for part of the spectrum in the 2000 nm region, corresponding toless than six optical cycles, was achieved. A heterodyne measurement of thefree-running mode-locked laser with a narrow-linewidth continuous wave laserresulted in a near shot noise-limited beat note with a signal-to-noise ratio of45 dB in a 10 kHz resolution bandwidth. The relative intensity noise of thebroadband system was investigated over the entire supercontinuum, and theintegrated relative intensity noise of the 2000 nm portion of the spectrum was0.0017. The long-term stability of the system was characterized, and intensityfluctuations in the spectrum were found to be highly correlated throughout thesupercontinuum. Spectroscopic limitations due to the laser noisecharacteristics are discussed.