Near-infrared molecular spectroscopy using NICE-OHMS with high finesse cavity

Chen, TzuLing

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https://hdl.handle.net/2142/104493 Copy

Description

Title

Near-infrared molecular spectroscopy using NICE-OHMS with high finesse cavity

Author(s)

Chen, TzuLing

Contributor(s)

Liu, YiWei

Issue Date

2019-06-20

Keyword(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.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/104493

DOI

https://doi.org/10.15278/isms.2019.RL06

Copyright and License Information

Copyright 2019 TzuLing Chen

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