Graphics card-based real-time processing for dual comb interferometry.

The technique of performing interferometry with two optical frequency combs is used by an increasing number of research groups and even for field deployed commercial applications. Real-time interferogram acquisition, correction, and averaging are, however, still not broadly accessible. This limits the deployment and wider adoption of this high resolution, high sensitivity technique.

Pulse interaction induced systematic errors in dual comb spectroscopy.

Systematic errors are observed in dual comb spectroscopy when pulses from the two sources travel in a common fiber before interrogating the sample of interest. When sounding a molecular gas, these errors distort both the line shapes and retrieved concentrations. Simulations of dual comb interferograms based on a generalized nonlinear Schrodinger equation highlight two processes for these systematic errors.

Validation of open-path dual-comb spectroscopy against an O background: erratum.

This erratum corrects errors that appear in Opt. Express31, 5042 (2023).10.

Removing biases in dual frequency comb spectroscopy due to digitizer nonlinearity.

Operation of any dual-comb spectrometer requires digitization of the interference signal before further processing. Nonlinearities in the analog-to-digital conversion can alter the apparent gas concentration by multiple percent, limiting both precision and accuracy of this technique. This work describes both the measurement of digitizer nonlinearity and the development of a model that quantitatively describes observed concentration bias over a range of conditions.

Open-path dual-comb spectroscopy of methane and VOC emissions from an unconventional oil well development in Northern Colorado.

We present results from a field study monitoring methane and volatile organic compound emissions near an unconventional oil well development in Northern Colorado from September 2019 to May 2020 using a mid-infrared dual-comb spectrometer. This instrument allowed quantification of methane, ethane, and propane in a single measurement with high time resolution and integrated path sampling. Using ethane and propane as tracer gases for methane from oil and gas activity, we observed emissions during the drilling, hydraulic fracturing, millout, and flowback phases of well development.

Validation of open-path dual-comb spectroscopy against an O background.

Dual-comb spectroscopy measures greenhouse gas concentrations over kilometers of open air with high precision. However, the accuracy of these outdoor spectra is challenging to disentangle from the absorption model and the fluctuating, heterogenous concentrations over these paths. Relative to greenhouse gases, O concentrations are well-known and evenly mixed throughout the atmosphere.

Experimental Constraint on Axionlike Particles over Seven Orders of Magnitude in Mass.

We use our recent electric dipole moment (EDM) measurement data to constrain the possibility that the HfF^{+} EDM oscillates in time due to interactions with candidate dark matter axionlike particles (ALPs). We employ a Bayesian analysis method which accounts for both the look-elsewhere effect and the uncertainties associated with stochastic density fluctuations in the ALP field. We find no evidence of an oscillating EDM over a range spanning from 27 nHz to 400 mHz, and we use this result to constrain the ALP-gluon coupling over the mass range 10^{-22}-10^{-15}  eV.

Precise multispecies agricultural gas flux determined using broadband open-path dual-comb spectroscopy.

Advances in spectroscopy have the potential to improve our understanding of agricultural processes and associated trace gas emissions. We implement field-deployed, open-path dual-comb spectroscopy (DCS) for precise multispecies emissions estimation from livestock. With broad atmospheric dual-comb spectra, we interrogate upwind and downwind paths from pens containing approximately 300 head of cattle, providing time-resolved concentration enhancements and fluxes of CH, NH, CO, and HO.

Dual-comb photoacoustic spectroscopy.

Spectrally resolved photoacoustic imaging is promising for label-free imaging in optically scattering materials. However, this technique often requires acquisition of a separate image at each wavelength of interest. This reduces imaging speeds and causes errors if the sample changes in time between images acquired at different wavelengths.

Compact mid-infrared dual-comb spectrometer for outdoor spectroscopy.

This manuscript describes the design of a robust, mid-infrared dual-comb spectrometer operating in the 3.1-µm to 4-µm spectral window for future field applications. The design represents an improvement in system size, power consumption, and robustness relative to previous work while also providing a high spectral signal-to-noise ratio.

Estimating vehicle carbon dioxide emissions from Boulder, Colorado, using horizontal path-integrated column measurements.

We performed 7.5 weeks of path-integrated concentration measurements of CO, CH, HO, and HDO over the city of Boulder, Colorado. An open-path dual-comb spectrometer simultaneously measured time-resolved data across a reference path, located near the mountains to the west of the city, and across an over-city path that intersected two-thirds of the city, including two major commuter arteries.

Dual-comb spectroscopy with tailored spectral broadening in SiN nanophotonics.

SiN waveguides, pumped at 1550 nm, can provide spectrally smooth, broadband light for gas spectroscopy in the important 2 μm to 2.5 μm atmospheric water window, which is only partially accessible with silica-fiber based systems. By combining Er fiber frequency combs and supercontinuum generation in tailored SiN waveguides, high signal-to-noise dual-comb spectroscopy spanning 2 μm to 2.

Femtosecond time synchronization of optical clocks off of a flying quadcopter.

Future optical clock networks will require free-space optical time-frequency transfer between flying clocks. However, simple one-way or standard two-way time transfer between flying clocks will completely break down because of the time-of-flight variations and Doppler shifts associated with the strongly time-varying link distances. Here, we demonstrate an advanced, frequency comb-based optical two-way time-frequency transfer (O-TWTFT) that can successfully synchronize the optical timescales at two sites connected via a time-varying turbulent air path.

Single-Blind Quantification of Natural Gas Leaks from 1 km Distance Using Frequency Combs.

A new method is tested in a single-blind study for detection, attribution, and quantification of methane emissions from the natural gas supply chain, which contribute substantially to annual U.S. emissions.

Open-path dual comb spectroscopy to an airborne retroreflector.

We demonstrate a new technique for spatial mapping of multiple atmospheric gas species. This system is based on high-precision dual-comb spectroscopy to a retroreflector mounted on a flying multi-copter. We measure the atmospheric absorption over long open-air paths to the multi-copter with comb-tooth resolution over 1.

Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers.

We present the first quantitative intercomparison between two open-path dual comb spectroscopy (DCS) instruments which were operated across adjacent 2-km open-air paths over a two-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6021 to 6388 cm (1565 to 1661 nm), corresponding to a 367 cm bandwidth, at 0.0067 cm sample spacing.

Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions.

We describe the first precision measurement of the electron's electric dipole moment (d_{e}) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on ^{180}Hf^{19}F^{+} in its metastable ^{3}Δ_{1} electronic state, we obtain d_{e}=(0.9±7.

Gas-phase broadband spectroscopy using active sources: progress, status, and applications.

Broadband spectroscopy is an invaluable tool for measuring multiple gas-phase species simultaneously. In this work we review basic techniques, implementations, and current applications for broadband spectroscopy. We discuss components of broad-band spectroscopy including light sources, absorption cells, and detection methods and then discuss specific combinations of these components in commonly-used techniques.

Room-temperature-deposited dielectrics and superconductors for integrated photonics.

We present an approach to fabrication and packaging of integrated photonic devices that utilizes waveguide and detector layers deposited at near-ambient temperature. All lithography is performed with a 365 nm i-line stepper, facilitating low cost and high scalability. We have shown low-loss SiN waveguides, high-Q ring resonators, critically coupled ring resonators, 50/50 beam splitters, Mach-Zehnder interferometers (MZIs) and a process-agnostic fiber packaging scheme.

Accurate frequency referencing for fieldable dual-comb spectroscopy.

We describe a dual-comb spectrometer that can operate independently of laboratory-based rf and optical frequency references but is nevertheless capable of ultra-high spectral resolution, high SNR, and frequency-accurate spectral measurements. The instrument is based on a "bootstrapped" frequency referencing scheme in which short-term optical phase coherence between combs is attained by referencing each to a free-running diode laser, whilst high frequency resolution and long-term accuracy is derived from a stable quartz oscillator. The sensitivity, stability and accuracy of this spectrometer were characterized using a multipass cell.

Mid-Infrared Time-Resolved Frequency Comb Spectroscopy of Transient Free Radicals.

We demonstrate time-resolved frequency comb spectroscopy (TRFCS), a new broadband absorption spectroscopy technique for the study of trace free radicals on the microsecond timescale. We apply TRFCS to study the time-resolved, mid-infrared absorption of the deuterated hydroxyformyl radical trans-DOCO, an important short-lived intermediate along the OD + CO reaction path. Directly after photolysis of the chemical precursor acrylic acid-d1, we measure absolute trans-DOCO product concentrations with a sensitivity of 5 × 10(10) cm(-3) and observe its subsequent loss with a time resolution of 25 μs.

Mid-infrared virtually imaged phased array spectrometer for rapid and broadband trace gas detection.

We present and characterize a two-dimensional (2D) imaging spectrometer based on a virtually imaged phased array (VIPA) disperser for rapid, high-resolution molecular detection using mid-infrared (MIR) frequency combs at 3.1 and 3.8 μm.

Frequency comb velocity-modulation spectroscopy.

We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity-modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF⁺ and achieved a fractional absorption sensitivity of 3×10⁻⁷ recorded over 1500 simultaneous channels spanning 150  cm⁻¹ around 800 nm with an absolute frequency accuracy of 30 MHz (0.001  cm⁻¹).

Mid-infrared Fourier transform spectroscopy with a broadband frequency comb.

We present a first implementation of optical-frequency-comb-based rapid trace gas detection in the molecular fingerprint region in the mid-infrared. Near-real-time acquisition of broadband absorption spectra with 0.0056 cm(-1) maximum resolution is demonstrated using a frequency comb Fourier transform spectrometer which operates in the 2100-to-3700-cm(-1) spectral region.