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

TL;DR

This paper reports a stable, tunable femtosecond light source near 2 μm created through supercontinuum generation from an erbium mode-locked laser, achieving broad spectrum, ultrashort pulses, and low noise for potential spectroscopic applications.

Contribution

The work demonstrates a stable, broad supercontinuum source near 2 μm with ultrashort pulses and low noise, advancing the development of femtosecond laser sources in this wavelength region.

Findings

Spectrum spans 1000 nm to 2200 nm with 250 mW power

Achieved 39 fs pulse width in the 2000 nm region

Relative intensity noise of 0.0017 in the 2000 nm spectrum

Abstract

A source of ultrashort pulses of light in the 2 {\mu}m region was constructed using supercontinuum broadening from an erbium mode-locked laser. The output spectrum spanned 1000 nm to 2200 nm with an average power of 250 mW. A pulse width of 39 fs for part of the spectrum in the 2000 nm region, corresponding to less than six optical cycles, was achieved. A heterodyne measurement of the free-running mode-locked laser with a narrow-linewidth continuous wave laser resulted in a near shot noise-limited beat note with a signal-to-noise ratio of 45 dB in a 10 kHz resolution bandwidth. The relative intensity noise of the broadband system was investigated over the entire supercontinuum, and the integrated relative intensity noise of the 2000 nm portion of the spectrum was 0.0017. The long-term stability of the system was characterized, and intensity fluctuations in the spectrum were found to be highly correlated throughout the supercontinuum. Spectroscopic limitations due to the laser noise characteristics are discussed.