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 Title: NEAR-INFRARED MOLECULAR SPECTROSCOPY USING NICE-OHMS WITH HIGH FINESSE CAVITY Author(s): Chen, TzuLing Contributor(s): Liu, YiWei Subject(s): Spectroscopy as an analytical tool Abstract: Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS), taking advantage of combining the cavity enhancement and frequency modulation techniques, provides an excellent method to enable ultra sensitive detection. The advantage of noise immunity enables for shot-noise limit detection, particularly for those molecules with ultra-small dipole moments, such as overtone transitions and symmetrical molecules, NICE-OHMS provides a superior strategy to achieve sub-Doppler saturation spectroscopy. Using an optical cavity with a high finesse $>$100,000, in our previous work, we reported the sub-Doppler saturation NICE-OHMS spectroscopy for nitrous oxide (\chem{N_2O}) overtone transitions using the quantum-dot (QD) laser developed at 1.28~$\mu$m. At a pressure of several mTorr, the saturation dip is observed with a full width at half-maximum of about 2~MHz. The noise equivalent bandwidth-reduced sensitivity is 1.6$\times$10$^{-11}$cm$^{-1}$Hz$^{-1/2}$. The QD laser is then locked to this dispersion signal with a stability of 15 kHz at 1 s integration time. We demonstrate the potential of the (\chem{N_2O}) as a marker because of its particularly rich spectrum in the vicinity of 1.28~$\mu$m, where there are several important forbidden transitions of atomic parity violation measurements. In current work, we have used a new QD laser system coupled to a high finesse cavity for NICE-OHMS of the \chem{H_2} overtone transition S1, where the dipole moment is only 30~mD. The QD laser developed at 1.16 $\mu$m is gain-chip based and mounted in an integrated mechanism system to reduce the passive laser linewidth. The cavity finesse was measured to be 234,000 (8000) by using laser-swept cavity ring-down time measurements. After the laser locking, the laser power will be amplified by a fiber amplifier to satisfy saturation condition to achieve sub-Doppler NICE-OHMS spectroscopy. Issue Date: 2019-06-20 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/104493 DOI: 10.15278/isms.2019.RL06 Rights Information: Copyright 2019 TzuLing Chen Date Available in IDEALS: 2019-07-152020-01-25
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