Photoacoustic dual-comb spectroscopy(DCS),converting spectral information in the optical frequency domain to the audio frequency domain via multi-heterodyne beating,enables background-free spectral measurements with high resolution and broad bandwidth.However,the detection sensitivity remains limited due to the low power of individual comb lines and the lack of broadband acoustic resonators.Here,we develop cavity-enhanced photoacoustic DCS,which overcomes these limitations by using a high-finesse optical cavity for the power amplification of dual-frequency combs and a broadband acoustic resonator with a flat-top frequency response.We demonstrate high-resolution spectroscopic measurements of trace amounts of C2H2,NH3 and CO in the entire telecommunications C-band.The method shows a minimum detection limit of 0.6 ppb C2H2 at the measurement time of 100 s,corresponding to the noise equivalent absorption coefficient of 7 × 10-10cm-1.The proposed cavity-enhanced photoacoustic DCS may open new avenues for ultrasensitive,high-resolution,and multi-species gas detection with widespread applications.
Zhen Wang、Qinxue Nie、Haojia Sun、Qiang Wang、Simone Borri、Paolo De Natale、Wei Ren
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Department of Mechanical and Automation Engineering,The Chinese University of Hong Kong,New Territories,Hong Kong SAR,China
State Key Laboratory of Applied Optics,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,130033 Changchun,China
CNR-INO—Istituto Nazionale di Ottica,and LENS—European Laboratory for Nonlinear Spectroscopy,50019 Sesto Fiorentino,Italy
General Research FundGeneral Research FundCollaborative Research Fund from the University Grants CommitteeInnovation and Technology Fund from the Innovation and Technology Commission,Hong Kong SAR,ChinaNational Natural Science Foundation of China(NSFC)National Natural Science Foundation of China(NSFC)National Natural Science Foundation of China(NSFC)
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