Showing papers on "Fourier transform spectroscopy published in 2017"
TL;DR: In this article, a combination of digital signal processing and broadband frequency conversion in waveguides is used to measure comb-tooth resolved spectra across an octave of bandwidth in the mid-infrared from 2.6-5.2
Abstract: Mid-infrared dual-comb spectroscopy has the potential to supplant conventional high-resolution Fourier transform spectroscopy in applications that require high resolution, accuracy, signal-to-noise ratio, and speed. Until now, dual-comb spectroscopy in the mid-infrared has been limited to narrow optical bandwidths or to low signal-to-noise ratios. Using a combination of digital signal processing and broadband frequency conversion in waveguides, we demonstrate a mid-infrared dual-comb spectrometer that can measure comb-tooth resolved spectra across an octave of bandwidth in the mid-infrared from 2.6-5.2 $\mu$m with sub-MHz frequency precision and accuracy and with a spectral signal-to-noise ratio as high as 6500. As a demonstration, we measure the highly structured, broadband cross-section of propane (C3H8) in the 2860-3020 cm-1 region, the complex phase/amplitude spectrum of carbonyl sulfide (COS) in the 2000 to 2100 cm-1 region, and the complex spectra of methane, acetylene, and ethane in the 2860-3400 cm-1 region.
191 citations
TL;DR: A novel type of Fourier Transform Spectrometer that can be realized with CMOS compatible fabrication techniques and is based on the direct detection of the interferogram generated by the interference of the evanescent fields of two co-propagating waveguide modes is demonstrated.
Abstract: We demonstrate a novel type of Fourier Transform Spectrometer (FTS) that can be realized with CMOS compatible fabrication techniques. This FTS contains no moving components and is based on the direct detection of the interferogram generated by the interference of the evanescent fields of two co-propagating waveguide modes. The theoretical analysis indicates that this type of FTS inherently has a large bandwidth (>100 nm). The first prototype that is integrated on a Si3N4 waveguide platform is demonstrated and has an extremely small size (0.1 mm2). We introduce the operation principle and report on the preliminary experiments. The results show a moderately high resolution (6 nm) which is in good agreement with the theoretical prediction.
61 citations
TL;DR: In this paper, dual-comb spectroscopy is extended to the 6-8 µm wavelength band using femtosecond optical parametric oscillators (OPOs) in order to obtain high-fidelity spectra of H2O and CH4 at approximately 0.3 cm−1 resolutions.
Abstract: The new material orientation patterned gallium phosphide (OPGaP) enables coherent and broadband infrared spectroscopy in the spectral fingerprint region from 6 to 12 µm, accessing the largest molecular absorption cross-sections and permitting sensitive, quantitative and species-specific measurements. Here, we show how dual-comb spectroscopy—a form of high-speed Fourier-transform spectroscopy involving no moving parts and capable of very high resolutions—can be extended to the 6–8 µm wavelength band using femtosecond optical parametric oscillators (OPOs). By acquiring dual-comb interferograms in a time comparable with the mutual decoherence time of the OPO combs we implement cross-correlation-based spectral averaging to obtain high-fidelity spectra of H2O and CH4 at approximately 0.3 cm−1 resolutions from 1285 to 1370 cm−1 and 1500–1585 cm−1.
58 citations
01 Jan 2017
TL;DR: In this paper, the basic theory behind FTIR spectroscopy and its various instrumentation aspects are reviewed, and the characteristic vibrational absorption bands used for the identification of key chemical structures as well as methods for quantitative measurement of chemical composition are described.
Abstract: Infrared spectroscopy has always been a powerful tool for the identification of organic materials The development of Fourier transform infrared (FTIR) spectroscopy has introduced a popular method for the quantitative analysis of complex mixtures, as well as for the investigation of surface and interfacial phenomena This chapter reviews the basic theory behind FTIR spectroscopy and its various instrumentation aspects The characteristic vibrational absorption bands used for the identification of key chemical structures as well as methods for quantitative measurement of chemical composition are described here The advantages and disadvantages encountered while using FTIR are also reviewed here
51 citations
TL;DR: In this paper, the authors proposed a coherent Raman scattering (CRS) spectroscopy technique capable of acquiring 50,000 broadband Raman spectra/s by employing a Fourier-domain delay line based on a rapidly rotating polygonal mirror array as an optical path-length scanner.
51 citations
TL;DR: An alternative application of the Fourier transform spectroscopy (FTS) principles and techniques is proposed in this paper, where registration of hyperspectral holograms in incoherent light by using FTS is suggested.
Abstract: An alternative application of the Fourier transform spectroscopy (FTS) principles and techniques is proposed. Registration of hyperspectral holograms in incoherent light by using FTS is suggested. This work generalizes and develops our previous results on registration of hyperspectral Fresnel’s and image plane holograms. Theoretical and experimental results are provided and discussed. The proposed method is applied to the problems of digital holographic microscopy, including speckle noise reduction, hyperspectral imaging, and coloring and optical profiling. A major advantage of the proposed method is that it allows simultaneous recovery of the amplitude, the phase, and the spectral frequency σ of the wave field in a single registration process.
45 citations
TL;DR: In this article, the authors used a nanooctahedron CeO2 catalyst (Cu-CeO2-O) for the water-gas shift (WGS) reaction.
Abstract: CeO2 nanooctahedrons, nanorods, and nanocubes were prepared by the hydrothermal method and were then used as supports of Cu-based catalysts for the water-gas shift (WGS) reaction. The chemical and physical properties of these catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS) techniques. Characterization results indicate that the morphology of the CeO2 supports, originating from the selective exposure of different crystal planes, has a distinct impact on the dispersion of Cu and the catalytic properties. The nanooctahedron CeO2 catalyst (Cu-CeO2-O) showed the best dispersion of Cu, the largest amount of moderate copper oxide, and the strongest Cu-support interaction. Consequently, the Cu-CeO2-O catalyst exhibited the highest CO conversion at the temperature range of 150–250 °C when compared with the nanocube and nanorod Cu-CeO2 catalysts. The optimized Cu content of the Cu-CeO2-O catalysts is 10 wt % and the CO conversion reaches 91.3% at 300 °C. A distinctive profile assigned to the evolution of different types of carbonate species was observed in the 1000–1800 cm−1 region of the in situ DRIFTS spectra and a particular type of carbonate species was identified as a potential key reaction intermediate at low temperature.
44 citations
TL;DR: In this paper, a simple one-step mechanochemical synthesis method with a green chemistry approach for a light-induced heterogeneous oxide photocatalyst, ZnSnO 3, was reported.
42 citations
TL;DR: This work presents a generalised method for extracting complex refractive indices of aqueous solutions in the mid-infrared region using conventional attenuated total reflection Fourier transform spectroscopy (ATR-FTIR) without the need for collimated or polarised incident light, as is required for existing methods.
Abstract: Mid-infrared (MIR) spectroscopy is a powerful tool for characterising the vibrations of molecular bonds and is therefore ideal for label-free detection of chemical species. Recent research into thin-film deposition and etching techniques for mid-infrared materials shows potential for realising miniaturised bedside biosensors for clinical diagnostics exploiting MIR spectroscopy, to replace laboratory based-techniques. However, lack of refractive index information for commonly encountered biological media and analytes hampers optimisation of biosensor performance for maximum sensitivity, especially for devices exploiting evanescent spectroscopy. Here we present refractive index data for human whole blood and several aqueous solutions of general interest to the clinical community: anticoagulants, analgesics and buffers. The refractive indices are generally dominated by the water content of each sample and the whole blood spectra exhibit additional strong features due to protein content. Furthermore, we present a generalised method for extracting complex refractive indices of aqueous solutions in the mid-infrared region using conventional attenuated total reflection Fourier transform spectroscopy (ATR-FTIR) without the need for collimated or polarised incident light, as is required for existing methods.
37 citations
TL;DR: It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodsal line slope is independent of excited state parameters not known from the absorption and emission spectra.
Abstract: Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distribution determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. The absorption...
36 citations
Abstract: Spectroscopic ellipsometry is a means to investigate optical and dielectric material responses. Conventional spectroscopic ellipsometry has trade-offs between spectral accuracy, resolution, and measurement time. Polarization modulation has afforded poor performance due to its sensitivity to mechanical vibrational noise, thermal instability, and polarization wavelength dependency. We equip a spectroscopic ellipsometer with dual-optical-comb spectroscopy, viz. dual-optical-comb spectroscopic ellipsometry (DCSE). The DCSE directly and simultaneously obtains amplitude and phase information with ultra-high spectral precision that is beyond the conventional limit. This precision is due to the automatic time-sweeping acquisition of the interferogram using Fourier transform spectroscopy and optical combs with well-defined frequency. Ellipsometric evaluation without polarization modulation also enhances the stability and robustness of the system. In this study, we evaluate the DCSE of birefringent materials and thin films, which showed improved spectral accuracy and a resolution of up to 1.2x10-5 nm across a 5-10 THz spectral bandwidth without any mechanical movement.
TL;DR: Using paired coherent frequency combs for broadband molecular spectroscopy can provide dramatic gains in spectral resolution, sensitivity and data acquisition speed as mentioned in this paper, and may help take the power of frequency comb spectrograms out of the lab and into the field.
Abstract: Using paired coherent frequency combs for broadband molecular
spectroscopy can provide dramatic gains in spectral resolution, sensitivity and data acquisition speed-and may help take the power of frequency comb spectroscopy out of the lab and into the field.
TL;DR: In this article, the authors presented the first open-path near-infrared FTS measurements of CO2, CH4, O2, H2O and HDO over a 1.5 km path in urban Heidelberg, Germany.
Abstract: . In complex and urban environments, atmospheric trace gas composition is highly variable in time and space. Point measurement techniques for trace gases with in situ instruments are well established and accurate, but do not provide spatial averaging to compare against developing high-resolution atmospheric models of composition and meteorology with resolutions of the order of a kilometre. Open-path measurement techniques provide path average concentrations and spatial averaging which, if sufficiently accurate, may be better suited to assessment and interpretation with such models. Open-path Fourier transform spectroscopy (FTS) in the mid-infrared region, and differential optical absorption spectroscopy (DOAS) in the UV and visible, have been used for many years for open-path spectroscopic measurements of selected species in both clean air and in polluted environments. Near infrared instrumentation allows measurements over longer paths than mid-infrared FTS for species such as greenhouse gases which are not easily accessible to DOAS. In this pilot study we present the first open-path near-infrared (4000–10 000 cm−1, 1.0–2.5 µm) FTS measurements of CO2, CH4, O2, H2O and HDO over a 1.5 km path in urban Heidelberg, Germany. We describe the construction of the open-path FTS system, the analysis of the collected spectra, several measures of precision and accuracy of the measurements, and the results a four-month trial measurement period in July–November 2014. The open-path measurements are compared to calibrated in situ measurements made at one end of the open path. We observe significant differences of the order of a few ppm for CO2 and a few tens of ppb for CH4 between the open-path and point measurements which are 2 to 4 times the measurement repeatability, but we cannot unequivocally assign the differences to specific local sources or sinks. We conclude that open-path FTS may provide a valuable new tool for investigations of atmospheric trace gas composition in complex, small-scale environments such as cities.
TL;DR: This work characterize 16000 longitudinal cavity modes spanning 16 THz of bandwidth in terms of center frequency, linewidth, and amplitude and retrieves the group delay dispersion of the cavity mirror coatings and pure N2 with 0.1 fs2 precision and 1 fs2 accuracy.
Abstract: Optical cavities provide high sensitivity to dispersion since their resonance frequencies depend on the index of refraction We present a direct, broadband, and accurate measurement of the modes of a high finesse cavity using an optical frequency comb and a mechanical Fourier transform spectrometer with a kHz-level resolution We characterize 16000 longitudinal cavity modes spanning 16 THz of bandwidth in terms of center frequency, linewidth, and amplitude Using the center frequencies we retrieve the group delay dispersion of the cavity mirror coatings and pure N2 with 01 fs2 precision and 1 fs2 accuracy, as well as the refractivity of the 3ν1 + ν3 absorption band of CO2 with 5 × 10−12 precision This opens up for broadband refractive index metrology and calibration-free spectroscopy of entire molecular bands
TL;DR: A compact, fast and versatile Fourier-transform spectrometer, combining absorption and excitation-emission fluorescence spectroscopy in the visible, generating phase-locked excitation pulse pairs via an inherently stable birefringent wedge-based common-path interferometer.
Abstract: The correlation of molecular excitation and emission events provides a powerful multidimensional spectroscopy tool, by relating transitions from electronic ground and excited states through two-dimensional excitation-emission maps. Here we present a compact, fast and versatile Fourier-transform spectrometer, combining absorption and excitation-emission fluorescence spectroscopy in the visible. We generate phase-locked excitation pulse pairs via an inherently stable birefringent wedge-based common-path interferometer, retaining all the advantages of Fourier-transform spectroscopy but avoiding active stabilization or auxiliary tracking beams. We employ both coherent and incoherent excitation sources on dye molecules in solution, with data acquisition times in the range of seconds and minutes, respectively.
TL;DR: Campargue et al. as discussed by the authors reported accurate laboratory determination of the near infrared water vapor self-continuum: a test of the MT_CKD model, using Cavity Ring-down Spectroscopy (CRDS) and Optical Feedback-Cavity Enhanced Absorption Spectrograph (OF-CEAS) at selected spectral points of 4 near infrared transparency windows.
Abstract: In a recent contribution [A. Campargue, S. Kassi, D. Mondelain, S. Vasilchenko, D. Romanini, Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model. J. Geophys. Res. Atmos., 121,13,180–13,203, doi:10.1002/2016JD025531], we reported accurate water vapor absorption continuum measurements by Cavity Ring-down Spectroscopy (CRDS) and Optical-Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) at selected spectral points of 4 near infrared transparency windows. In the present work, the self-continuum cross-sections, CS, are determined for two new spectral points. The 2491 cm−1 spectral point in the region of maximum transparency of the 4.0 µm window was measured by OF-CEAS in the 23–52 °C temperature range. The 4435 cm−1 spectral point of the 2.1 µm window was measured by CRDS at room temperature. The self-continuum cross-sections were determined from the pressure squared dependence of the continuum absorption. Comparison to the literature shows a reasonable agreement with 1970 s and 1980 s measurements using a grating spectrograph in the 4.0 µm window and a very good consistency with our previous laser measurements in the 2.1 µm window. For both studied spectral points, our values are much smaller than previous room temperature measurements by Fourier Transform Spectroscopy. Significant deviations (up to about a factor 4) are noted compared to the widely used semi empirical MT_CKD model of the absorption continuum. The measured temperature dependence at 2491 cm−1 is consistent with previous high temperature measurements in the 4.0 µm window and follows an exp(D0/kT) law, D0 being the dissociation energy of the water dimer.
TL;DR: A birefringent interferometer for FT spectroscopy is demonstrated based on the Translating-Wedge-based Identical pulses eNcoding System with alpha barium borate and lithium niobate, however the transparency of these crystals does not extend to the mid-IR fingerprint region.
Abstract: We introduce a birefringent interferometer for Fourier transform (FT) spectroscopy in the mid-infrared, covering the vibrational fingerprint region (5-10 µm, 1000-2000 cm−1), which is crucial for molecular identification. Our interferometer employs the crystal calomel (Hg2Cl2), which combines high birefringence (ne-no≈0.55) with a broad transparency range (0.38-20 µm). We adopt a design based on birefringent wedges, which is simple and compact and guarantees excellent delay accuracy and long-term stability. We demonstrate FTIR spectroscopy, with a frequency resolution of 3 cm−1, as well as two-dimensional IR (2DIR) spectroscopy. Our setup can be extended to other spectroscopic modalities such as vibrational circular dichroism and step-scan FT spectroscopy.
TL;DR: The step-scan differential Fourier transform infrared photoacoustic spectroscopy method was demonstrated to be an effective approach for monitoring weakly absorbing gases with absorption bands overlapped by strongly absorbing background species.
Abstract: The determination of small absorption coefficients of trace gases in the atmosphere constitutes a challenge for analytical air contaminant measurements, especially in the presence of strongly absorbing backgrounds. A step-scan differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS) method was developed to suppress the coherent external noise and spurious photoacoustic (PA) signals caused by strongly absorbing backgrounds. The infrared absorption spectra of acetylene (C2H2) and local air were used to verify the performance of the step-scan DFTIR-PAS method. A linear amplitude response to C2H2 concentrations from 100 to 5000 ppmv was observed, leading to a theoretical detection limit of 5 ppmv. The differential mode was capable of eliminating the coherent noise and dominant background gas signals, thereby revealing the presence of the otherwise hidden C2H2 weak absorption. Thus, the step-scan DFTIR-PAS modality was demonstrated to be an effective approach for monitoring weakly absorbing gases with absorption bands overlapped by strongly absorbing background species.
TL;DR: A Fourier transform spectroscopy technique for directly measuring band structures, and applies it to a spin-1 spin–orbit coupled Bose–Einstein condensate, to reconstruct the spin and momentum resolved spectrum from the peak frequencies of the Fourier transformed populations.
Abstract: We describe a Fourier transform spectroscopy technique for directly measuring band structures, and apply it to a spin-1 spin-orbit coupled Bose-Einstein condensate. In our technique, we suddenly change the Hamiltonian of the system by adding a spin-orbit coupling interaction and measure populations in different spin states during the subsequent unitary evolution. We then reconstruct the spin and momentum resolved spectrum from the peak frequencies of the Fourier transformed populations. In addition, by periodically modulating the Hamiltonian, we tune the spin-orbit coupling strength and use our spectroscopy technique to probe the resulting dispersion relation. The frequency resolution of our method is limited only by the coherent evolution timescale of the Hamiltonian and can otherwise be applied to any system, for example, to measure the band structure of atoms in optical lattice potentials.
TL;DR: A novel, compact gas measurement system using a static single-mirror Fourier transform spectrometer (sSMFTS), which permits measurement rates of up to 200 Hz and high signal-to-noise ratios, and an application in process analysis appears promising.
Abstract: Online monitoring of gases in industrial processes is an ambitious task due to adverse conditions such as mechanical vibrations and temperature fluctuations. Whereas conventional Fourier transform infrared (FTIR) spectrometers use rather complex optical and mechanical designs to ensure stable operation, static FTIR spectrometers do not require moving parts and thus offer inherent stability at comparatively low costs. Therefore, we present a novel, compact gas measurement system using a static single-mirror Fourier transform spectrometer (sSMFTS). The system works in the mid-infrared range from 650 cm - 1 to 1250 cm - 1 and can be operated with a customized White cell, yielding optical path lengths of up to 120 cm for highly sensitive quantification of gas concentrations. To validate the system, we measure different concentrations of 1,1,1,2-Tetrafluoroethane (R134a) and perform a PLS regression analysis of the acquired infrared spectra. Thereby, the measured absorption spectra show good agreement with reference data. Since the system additionally permits measurement rates of up to 200 Hz and high signal-to-noise ratios, an application in process analysis appears promising.
TL;DR: The water vapour line broadening (γ) and shifting coefficients for 212 lines of eight vibrational bands, namely, ν2 + ν3, 2ν2
Abstract: The water vapour line broadening (γ) and shifting (δ) coefficients for 212 lines of eight vibrational bands, namely, ν2 + ν3, 2ν2 + ν3, 3ν2 + ν3–ν2, 4ν2, ν1 + ν3, ν1 + ν2, ν1 + 2ν2 and 2ν1, in the ...
TL;DR: In this paper, the high-resolution B1Σ+→A1Π (0, 0) and ( 0, 3) emission bands of the less-abundant 13C17O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy of 0.003 cm-1.
Abstract: The high-resolution B1Σ+→A1Π (0, 0) and (0, 3) emission bands of the less-abundant 13C17O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm-1. These spectra are combined with high-resolution photoabsorption measurements of the 13C17O B1Σ+←X1Σ+ (0, 0), B1Σ+←X1Σ+ (1, 0) and C1Σ+←X1Σ+ (0, 0) bands recorded with an accuracy of 0.01 cm-1 using the vacuum ultraviolet Fourier-transform spectrometer, installed on the DESIRS beamline at the SOLEIL synchrotron. In the studied 17,950–22,500 cm-1 and 86,800–92,100 cm-1 regions, 480 transitions have been measured. These new experimental data were combined with data from the C→A and B→A systems, previously analyzed in 13C17O. The frequencies of 1003 transitions derived from 12 bands were used to analyze the perturbations between the A1Π (υ=0–3) levels and rovibrational levels of the d3Δi, e3Σ-, a'3Σ+, I1Σ- and D1Δ states as well as to a preliminary investigation of weak irregularities that appear in the B1Σ+ (υ=0) level. Deperturbed molecular constants and term values of the A1Π state were obtained. The spin-orbit and L-uncoupling interaction parameters as well as isotopologue-independent spin-orbit and rotation-electronic perturbation parameters were derived.
TL;DR: In this article, near infrared spectroscopy is used for bacterial analysis, and it brings benefits over other vibrational approaches; the benefits over vibrational approach, however, are limited.
Abstract: Infrared spectroscopy is a prominent molecular technique for bacterial analysis. Within its context, near infrared spectroscopy in particular brings benefits over other vibrational approaches; thes...
TL;DR: In this article, the authors used attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) and partial least squares (PLS) algorithm for the determination of total isothiocyanate content in broccoli.
TL;DR: The influence of activation parameters on the process and extent of alkali activation of slag under ambient and elevated temperature curing, evaluated through spectroscopic techniques, is reported in this paper.
Abstract: The use of waste/by-product materials, such as slag or fly ash, activated using alkaline agents to create binding materials for construction applications (in lieu of portland cement) is on the rise. The influence of activation parameters (SiO2 to Na2O ratio or Ms of the activator, Na2O to slag ratio or n, cation type K+ or Na+) on the process and extent of alkali activation of slag under ambient and elevated temperature curing, evaluated through spectroscopic techniques, is reported in this paper. Fourier transform infrared spectroscopy along with a Fourier self-deconvolution method is used. The major spectral band of interest lies in the wavenumber range of ∼950 cm-1, corresponding to the antisymmetric stretching vibration of Si-O-T (T = Si or Al) bonds. The variation in the spectra with time from 6 h to 28 days is attributed to the incorporation of Al in the gel structure and the enhancement in degree of polymerization of the gel. 29Si nuclear magnetic resonance spectroscopy is used to quantify the Al incorporation with time, which is found to be higher when Na silicate is used as the activator. The Si-O-T bond wavenumbers are also generally lower for the Na silicate activated systems.
TL;DR: In this paper, LiSr was produced in a heat-pipe oven and its thermal emission spectrum around 9300 cm−1 was recorded by a high-resolution Fourier transform spectrometer.
Abstract: LiSr was produced in a heat-pipe oven and its thermal emission spectrum around 9300 cm−1 was recorded by a high resolution Fourier transform spectrometer. In addition, selected lines of the spectrum of deeply bound vibrational levels of the and states were studied using laser excitation to facilitate the assignment of the lines. The ground state could be described for to 2, up to 105 and the state for up to . For both states, Dunham coefficients, spin–rotation parameters and potential energy curves were evaluated. A coupling of the state to the state was observed, allowing a local description with Dunham coefficients of the state and an approximate evaluation of the coupling strength.
20 Jun 2017
TL;DR: In this article, two-dimensional Fourier transform spectroscopy can be adapted to evaluate spin splitting of ground-state electrons in complex quantum-mechanical systems, but resolving energy splitting on megahertz scales remains a challenge.
Abstract: Multidimensional coherent optical spectroscopy is currently one of the most powerful tools for investigating complex quantum-mechanical systems, but resolving energy splitting on megahertz scales remains a challenge. A new investigation shows how two-dimensional Fourier transform spectroscopy can be adapted to evaluate spin splitting of ground-state electrons.
TL;DR: An extension of this method is reported for local spectroscopic characterization of transparent samples and in particular for the determination of depth-resolved reflectance spectra of buried interfaces.
Abstract: Full-field optical coherence tomography (FF-OCT) is a widely used technique for applications such as biological imaging, optical metrology, and materials characterization, providing structural and spectral information. By spectral analysis of the backscattered light, the technique of spectroscopic-OCT enables the differentiation of structures having different spectral properties, but not the determination of their reflectance spectrum. For surface measurements, this can be achieved by applying a Fourier transform to the interferometric signals and using an accurate calibration of the optical system. An extension of this method is reported for local spectroscopic characterization of transparent samples and in particular for the determination of depth-resolved reflectance spectra of buried interfaces. The correct functioning of the method is demonstrated by comparing the results with those obtained using a program based on electromagnetic matrix methods for stratified media. Experimental measurements of spatial resolutions are provided to demonstrate the smallest structures that can be characterized.