AI Article Synopsis
- Frequency combs are powerful tools for precise and quick molecular spectroscopy, often created using difference frequency generation (DFG) from near-infrared sources, but measuring their coherence properties has been underexplored.
- This study focuses on a Raman-soliton based DFG source powered by a Yb:fiber comb, measuring coherence through a heterodyne beat between DFG and Tm:fiber frequency combs.
- Results show a sub-Hz relative linewidth between the two combs, and a new locking mechanism using interferometry is introduced for stabilizing intensity noise over long periods.
Article Abstract
Frequency combs present a unique tool for high-precision and rapid molecular spectroscopy. Difference frequency generation (DFG) of near-infrared sources is a common approach to generate passively stabilized mid-infrared combs. However, only little attention has been paid so far to precisely measure the coherence properties of such sources. Here, we investigate these using a Raman-soliton based DFG source driven by an Yb:fiber frequency comb. A heterodyne beat between the second harmonic of the phase-locked DFG comb near 4 µm and a 2 µm Tm:fiber frequency comb locked to the same optical reference is performed. Using this method, we measure the relative phase noise power spectral density of both combs. This results in a sub-Hz relative linewidth between the DFG comb and the Tm:fiber comb. We also introduce a new pump/seed delay locking mechanism based on interferometry for long-term stable intensity noise suppression.
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| http://dx.doi.org/10.1364/OL.491684 | DOI Listing |
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