Comb coherence-transfer and cavity ring-down saturation spectroscopy around 1.65 μm: kHz-accurate frequencies of transitions in the 2ν₃ band of ¹²CH₄

Abstract

Comb Coherence Transfer (CCT) uses a feed-forward frequency correction to transfer the optical phase of a frequency comb to the beam of a free-running diode laser. This allows to amplify...

12CO2 transition frequencies with kHz-accuracy by saturation spectroscopy in the 1.99–2.09 μm region

“…As already reported 37,40,43,44 in the case of a saturated line profile, the ring down signals are no more a purely decreasing exponential with time. In Giusfredi et al , 37 a non-exponential model was proposed to fit the ring down events and to obtain more reliable Lamb dip profiles.…”

“…In our previous works, 4,32,39 a beat note (BN) signal, between the laser source and the closest tooth of a frequency comb (FC), was used to accurately determine the absolute frequency of the laser source, limited by a laser line width of a few hundred kHz. Here, this signal is used to transfer the coherence of the comb to a fraction of the ECDL output using the feed-forward technique, described in Votava et al 40 and in Gotti et al, 41 providing a driftless and spectrally narrower source directly tunable using a RF synthesizer. In more detail, the BN signal is first low-pass filtered (BLP-150+ from Mini-Circuits; 150 MHz cut-off) to select only the BN with the closest comb tooth, amplified with a series of three amplifiers (ZFL500LN+ from Mini-Circuits; 28 dB of gain), and then separated with a power splitter (PSC-2-1 from Mini-Circuits; 0.1 to 400 MHz).…”

The (2–0) R(0) and R(1) transition frequencies of HD determined to a 10−10 relative accuracy by Doppler spectroscopy at 80 K

“…ref. 37) and a Lorenzian fit was performed to determine the center of the Lamb dip. From the 247 determinations, an average center value of 214904329.8263(15) MHz or 7168.43683327(5) cm À1 was determined i.e.…”

Absolute frequency metrology of buffer-gas-cooled molecular spectra at the 10-12 accuracy level

“…In this configuration, we address the acetylene (ν 1 +ν 3 ) R(1)e ro-vibrational line at 6561.0941 cm −1 in a 20-K cell specimen, demonstrating absolute line-center frequency measurements with an overall (statistical + systematic) fractional uncertainty as low as 6 × 10 −12 . In fact, by equaling the highest accuracy levels obtained so far with long-standing methodologies involving room-temperature samples [25][26][27][28][29][30], our achievement marks the birth of frequency metrology on cold spectra.…”