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arXiv · 0912.2683

Observing the intrinsic linewidth of a quantum-cascade laser: beyond the Schawlow-Townes limit

S. Bartalini·S. Borri·P. Cancio·A. Castrillo·I. Galli·G. Giusfredi·D. Mazzotti·L. Gianfrani·P. De Natale
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Abstract

A comprehensive investigation of the frequency-noise spectral density of a free-running mid-infrared quantum-cascade laser is presented for the first time. It provides direct evidence of the leveling of this noise down to a white noise plateau, corresponding to an intrinsic linewidth of a few hundred Hz. The experiment is in agreement with the most recent theory on the fundamental mechanism of line broadening in quantum-cascade lasers, which provides a new insight into the Schawlow-Townes formula and predicts a narrowing beyond the limit set by the radiative lifetime of the upper level.

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S. Bartalini, S. Borri, P. Cancio, A. Castrillo, I. Galli, G. Giusfredi, D. Mazzotti, L. Gianfrani, P. De Natale. 2010-02-11. Observing the intrinsic linewidth of a quantum-cascade laser: beyond the Schawlow-Townes limit. https://doi.org/10.1103/physrevlett.104.083904

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