Measurement of the intrinsic linewidth of terahertz quantum cascade lasers using a near- infrared frequency comb

Marco Ravaro (1) , Stefano Barbieri (1) , Giorgio Santarelli (2) , Vishal Jagtap (1) , Christophe Manquest (1) , Carlo Sirtori (1) , Suraj P. Khanna (3) , Edmund H. Linfield (4)

1 MPQ (UMR_7162) - Laboratoire Matériaux et Phénomènes Quantiques
2 lp2n-06,lp2n-14
3 School of Electronic and Electrical Engineering
4 School of Electronics and Electrical Engineering

We report the measurement of the frequency noise power spectral density of a quantum cascade laser emitting at 2.5THz. The technique is based on heterodyning the laser emission frequency with a harmonic of the repetition rate of a near-infrared laser comb. This generates a beatnote in the radio frequency range that is demodulated using a tracking oscillator allowing measurement of the frequency noise. We find that the latter is strongly affected by the level of optical feedback, and obtain an intrinsic linewidth of ~230Hz, for an output power of 2mW.

Mots clés: Infrared and far-infrared lasers; Semiconductor lasers; quantum cascade; Coherence; Infrared and far-infrared lasers.

Domaines: Optique [physics.optics]

Marco Ravaro, Stefano Barbieri, Giorgio Santarelli, Vishal Jagtap, Christophe Manquest, et al.. Measurement of the intrinsic linewidth of terahertz quantum cascade lasers using a near- infrared frequency comb. Optics Express, 2012, 20 (23), pp.25654-25661. ⟨10.1364/OE.20.025654⟩. ⟨hal-00813600⟩