A quantum cascade laser-based mid-IR frequency metrology system with ultra-narrow linewidth and $1\times 10^{-13}$-level frequency instability

Abstract

We demonstrate a powerful tool for high-resolution mid-IR spectroscopy and frequency metrology with quantum cascade lasers (QCLs). We have implemented frequency stabilization of a QCL to an ultra-low expansion (ULE) reference cavity, via upconversion to the near-IR spectral range, at a level of $1\times 10^{-13}$. The absolute frequency of the QCL is measured relative to a hydrogen maser, with instability $<1\times 10^{-13}$ and inaccuracy $5\times 10^{-13}$, using a frequency comb phase-stabilized to an independent ultrastable laser. The QCL linewidth is determined to be 60 Hz, dominated by fiber noise. Active suppression of fiber noise could result in sub-10 Hz linewidth.

References in corpus (2)

• A compact, robust, and transportable ultra-stable laser with a fractional frequency instability of $1\times 10^{-15}$
• A widely tunable 10-$\mu$m quantum cascade laser phase-locked to a state-of-the-art mid-infrared reference for precision molecular spectroscopy

Cited by in corpus (2)

• QCL-based frequency metrology from the mid-infrared to the THz range: a review
• Laser spectroscopy of cold molecules