A simple and easy to use method that allows high-finesse optical cavities to be used as absorption cells for spectroscopic purposes is presented. This method introduces a single-mode continuous-wave laser into the cavity by use of an off-axis cavity alignment geometry to eliminate systematically the resonances commonly associated with optical cavities, while preserving the absorption signal amplifying properties of such cavities. This considerably reduces the complexity of the apparatus compared with other high-resolution cavity-based absorption methods. Application of this technique in conjunction with either cavity ringdown spectroscopy or integrated cavity output spectroscopy produced absorption sensitivities of 1.5 x 10(-9) cm(-1) Hz(-1/2) and 1.8 x 10(-10) cm(-1) Hz(-1/2), respectively.
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http://dx.doi.org/10.1364/ao.40.004904 | DOI Listing |
J Phys Chem A
January 2025
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
We present direct frequency comb cavity ring-down spectroscopy with Vernier filtering as a straightforward approach to sensitive and multiplexed trace gas detection. The high finesse cavity acts both to extend the interaction length with the sample and as a spectral filter, alleviating the need for dispersive elements or an interferometer. In this demonstration, a free running interband cascade laser was used to generate a comb centered at 3.
View Article and Find Full Text PDFAnal Chem
January 2025
Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China.
Detection of trace gases, such as radioactive carbon dioxide, clumped isotopes, and reactive radicals, is of great interest and poses significant challenges in various fields. Achieving both high selectivity and high sensitivity is essential in this context. We present a highly selective molecular spectroscopy method based on comb-locked, mid-infrared, cavity-enhanced, two-photon absorption.
View Article and Find Full Text PDFNat Commun
October 2024
Department of Electrical Engineering, California Institute of Technology, Pasadena, CA, USA.
Optical solitons have long been of interest both from a fundamental perspective and because of their application potential. Both cubic (Kerr) and quadratic nonlinearities can lead to soliton formation, but quadratic solitons can practically benefit from stronger nonlinearity and achieve substantial wavelength conversion. However, despite their rich physics, quadratic cavity solitons have been used only for broadband frequency comb generation, especially in the mid-infrared.
View Article and Find Full Text PDFRev Sci Instrum
October 2024
Université Paris-Saclay, CNRS/IN3P3, IJCLab, 91405 Orsay, France.
The innovative mechanism of steady-state microbunching (SSMB) promises a potent light source, featuring high repetition rate and coherent radiation. The laser modulator, comprising an undulator and an optical enhancement cavity, is pivotal in SSMB. A high-finesse prototype optical enhancement cavity for SSMB with an average power of 55 kW is described in this paper.
View Article and Find Full Text PDFWe report the first, to our knowledge, observation of the nonlinear phenomenon known as modulation instability (MI) in a coherently driven fiber resonator pumped at 1972 nm. To compensate for the very high losses in this spectral region, we have integrated a thulium-doped fiber amplifier inside the cavity. Lower losses allow a lower MI threshold, leading to the observation of this phenomenon at a moderate input power.
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