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Supersonic engine development requires accurate and detailed measurements of fluidic and thermodynamic parameters to optimize engine designs and benchmark computational fluid dynamic (CFD) simulations. Here, we demonstrate that dual…
We propose a new Fourier-transform spectroscopy technique based on the rotational Doppler effect. The technique offers an application for optical vortex frequency combs, where each frequency component carries a unique amount of orbital…
Two techniques that employ equally spaced trains of optical pulses to map an optical high frequency into a low frequency modulation of the signal that can be detected in real time are compared. The development of phase-stable optical…
Spectroscopy has attracted much attention in molecular detection, biomolecular identification, and chemical analysis for providing accurate measurement. However, it is almost unable to distinguish different sources with overlapped…
Frequency comb based multidimensional coherent spectroscopy is a novel optical method that enables high resolution measurement in a short acquisition time. The method's resolution makes multidimensional coherent spectroscopy relevant for…
Mid-infrared microscopy is an important tool for biological analyses, allowing a direct probe of molecular bonds in their low energy landscape. In addition to the label-free extraction of spectroscopic information, the application of…
We use optical frequency comb Fourier transform spectroscopy to measure high-resolution spectra of iodomethane, CH$_3$I in the C-H stretch region from 2800 to 3160 cm$^{-1}$. The fast-scanning Fourier transform spectrometer with…
We present a novel approach to cavity ring-down spectroscopy utilizing an optical frequency comb as the direct probe of the Fabry-Perot cavity, coupled with a time-resolved Fourier transform spectrometer for parallel retrieval of ring-down…
Dual-comb spectroscopy is emerging as one of the most appealing applications of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs combined with the…
A Doppler broadening thermometry (DBT) instrument is built based on cavity ring-down spectroscopy (CRDS) for precise determination of the Boltzmann constant. Compared with conventional direct absorption methods, the high-sensitivity of CRDS…
Two semiconductor optical frequency combs consuming less than 1 W of electrical power are used to demonstrate high-sensitivity mid-infrared dual-comb spectroscopy in the important 3-4 $\mu$m spectral region. The devices are 4 millimeters…
Optical diffraction tomography (ODT) is a powerful non-invasive 3D imaging technique, but its combination with broadband light sources is difficult. In this study, we introduce ultrabroadband ODT, covering over 150 nm of visible spectral…
Quantitative spectroscopy has been used to measure accurately the Doppler-broadening of atomic transitions in $^{85}$Rb vapor. By using a conventional platinum resistance thermometer and the Doppler thermometry technique, we were able to…
Direct frequency-comb spectroscopy is used to probe the absolute frequencies of $6S_{1/2}$-$8S_{1/2}$ two-photon transitions of atomic cesium in hot vapor environment. By utilizing the coherent control method of temporally splitting the…
The ability to detect and identify molecules at high sensitivity without the use of labels or capture agents is important for medical diagnostics, threat identification, environmental monitoring, and basic science. Microtoroid optical…
Dual-comb spectroscopy enables broadband analysis of key molecules with unparalleled frequency resolution and exceptional signal-to-noise ratios across various spectral regions. However, fully harnessing its potential for broadband…
Cavity ring-down spectroscopy is a ubiquitous optical method used to study light-matter interactions with high resolution, sensitivity and accuracy. However, it has never been performed with the multiplexing advantages of direct frequency…
The generation of spectrally pure high-frequency microwave signals is a critical functionality in fundamental and applied sciences, including metrology and communications. The development of optical frequency combs has enabled the powerful…
Advances in high-resolution laser spectroscopy have enabled many scientific breakthroughs in physics, chemistry, biology and astronomy. Optical frequency combs have pushed measurement limits with ultrahigh-frequency accuracy and…
We analyze several possibilities for precisely measuring electronic transitions in atomic helium by the direct use of phase-stabilized femtosecond frequency combs. Because the comb is self-calibrating and can be shifted into the ultraviolet…