We report on cavity-enhanced second-harmonic generation of 488 nm radiation in a 5 mm long period... more We report on cavity-enhanced second-harmonic generation of 488 nm radiation in a 5 mm long periodically poled KTiOPO4 (PPKTP) crystal pumped by the output of a single-mode 976 nm semiconductor external cavity laser. At a pump laser output power of 660 mW, a mode-matching efficiency into an enhancement cavity of 65 % was observed. A maximum power of 156 mW at 488 nm was generated in the enhancement cavity of which 130 mW was coupled out. Under these pump laser conditions an overall optical conversion efficiency of 20 % and an overall electrical to optical efficiency of 9 % was measured. Both the spatial and spectral properties of the 488 nm beam are of very high quality. Typically, a near-diffraction-limited beam with M 2 <1.1 is produced with low astigmatism and little ellipticity.
We propose a scheme to reconstruct the state of a twomode Bose-Einstein condensate, with a given ... more We propose a scheme to reconstruct the state of a twomode Bose-Einstein condensate, with a given total number of atoms, using an atom interferometer that requires beam splitter, phase shift and non-ideal atom counting operations. The density matrix in the number-state basis can be computed directly from the probabilities of different counts for various phase shifts between the original modes, unless the beamsplitter is exactly balanced. Simulated noisy data from a two-mode coherent state is produced and the state is reconstructed, for 49 atoms. The error can be estimated from the singular values of the transformation matrix between state and probability data.
The recently proposed two-level atom bichromatic beam splitter has been shown theoretically to gi... more The recently proposed two-level atom bichromatic beam splitter has been shown theoretically to give exceptionally clean beam splitting in momentum space. In this paper, we investigate the first-order coherence property of this beam splitter, which is an important test of its usefulness in interferometric applications. We find that the beam splitter exhibits maximum fringe visibility of 0.3, which may be increased significantly through conditioning on certain variables. We then propose a type of atom interferometer based on this system, which has many desirable properties when compared with existing versions. ͓S1050-2947͑97͒08001-3͔
Isotopes in Environmental and Health Studies, 2006
Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based c... more Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based cavity ring-down spectroscopy (CRDS) are presented. The CRDS system achieved good precision, often better than 0.2 ‰, for 4 % CO 2 concentrations, and also achieved 0.15-0.25 ‰ precision in a 78 min measurement time with cryotrap-based pre-concentration of ambient CO 2 concentrations (360 ppmv). These results were obtained with a CRDS system possessing a data rate of 40 ring-downs per second and a loss measurement of 4.0 × 10 −11 cm −1 Hz −1/2. Subsequently, the measurement time has been reduced to under 10 min. This standard of performance would enable a variety of high concentration (3-10 %) isotopic measurements, such as medical human breath analysis or animal breath experiments. The extension of this ring-down to the 2 µm region would enable isotopic analysis at ambient concentrations, which, combined with the small size, robust design, and potential for frequent measurements at a remote site, make CRDS technology attractive for remote atmospheric measurement applications.
Methane source pinpointing and attribution is ever more important because of the vast network of ... more Methane source pinpointing and attribution is ever more important because of the vast network of natural gas distribution which has led to a very large emission sources. Ethane can be used as a tracer to distinguish gas sources between biogenic and natural gas. Having this measurement sensitive enough can even distinguish between gas distributors, or maturity through gas wetness. Here we present data obtained using a portable cavity ring-down spectrometer weighing less than 11 kg and consuming less than 35W that simultaneously measures methane and ethane with a raw 1-σ precision of 50ppb and 4.5ppb, respectively at 2 Hz. These precisions allow for a C 2 :C 1 ratio 1-σ measurement of <0.1% above 10ppm in a single measurement. Utilizing a second onboard laser allows for a high precision methane only mode used for surveying and pinpointing. This mode measures at a rate faster than 4Hz with a 1-σ precision of <3ppb. Because methane seepages are highly variable due to air turbulence and mixing right above the ground, correlations in the variations in C 2 H 6 and CH 4 are used to derive a source C 2 :C 1. Additional hardware is needed for steady state concentration measurements to reliably measure the C 2 :C 1 ratio instantaneously. Source discrimination data of local leaks and methane sources using this analysis method are presented. Additionally, two-dimensional plume snapshots are constructed using an integrated onboard GPS to visualize horizontal plane gas propagation.
Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant ... more Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant source distributions. These features create a scale separation between local sources and urban scale emissions estimates known as the Grey-Zone. Modern computational fluid dynamics (CFD) techniques provide a quasi-deterministic, physically based toolset to bridge the scale separation gap between source level dynamics, local measurements, and urban scale emissions inventories. CFD has the capability to represent complex building topography and capture detailed 3D turbulence fields in the urban boundary layer.
We report on cavity-enhanced second-harmonic generation of 488 nm radiation in a 5 mm long period... more We report on cavity-enhanced second-harmonic generation of 488 nm radiation in a 5 mm long periodically poled KTiOPO4 (PPKTP) crystal pumped by the output of a single-mode 976 nm semiconductor external cavity laser. At a pump laser output power of 660 mW, a mode-matching efficiency into an enhancement cavity of 65 % was observed. A maximum power of 156 mW at 488 nm was generated in the enhancement cavity of which 130 mW was coupled out. Under these pump laser conditions an overall optical conversion efficiency of 20 % and an overall electrical to optical efficiency of 9 % was measured. Both the spatial and spectral properties of the 488 nm beam are of very high quality. Typically, a near-diffraction-limited beam with M 2 <1.1 is produced with low astigmatism and little ellipticity.
We propose a scheme to reconstruct the state of a twomode Bose-Einstein condensate, with a given ... more We propose a scheme to reconstruct the state of a twomode Bose-Einstein condensate, with a given total number of atoms, using an atom interferometer that requires beam splitter, phase shift and non-ideal atom counting operations. The density matrix in the number-state basis can be computed directly from the probabilities of different counts for various phase shifts between the original modes, unless the beamsplitter is exactly balanced. Simulated noisy data from a two-mode coherent state is produced and the state is reconstructed, for 49 atoms. The error can be estimated from the singular values of the transformation matrix between state and probability data.
The recently proposed two-level atom bichromatic beam splitter has been shown theoretically to gi... more The recently proposed two-level atom bichromatic beam splitter has been shown theoretically to give exceptionally clean beam splitting in momentum space. In this paper, we investigate the first-order coherence property of this beam splitter, which is an important test of its usefulness in interferometric applications. We find that the beam splitter exhibits maximum fringe visibility of 0.3, which may be increased significantly through conditioning on certain variables. We then propose a type of atom interferometer based on this system, which has many desirable properties when compared with existing versions. ͓S1050-2947͑97͒08001-3͔
Isotopes in Environmental and Health Studies, 2006
Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based c... more Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based cavity ring-down spectroscopy (CRDS) are presented. The CRDS system achieved good precision, often better than 0.2 ‰, for 4 % CO 2 concentrations, and also achieved 0.15-0.25 ‰ precision in a 78 min measurement time with cryotrap-based pre-concentration of ambient CO 2 concentrations (360 ppmv). These results were obtained with a CRDS system possessing a data rate of 40 ring-downs per second and a loss measurement of 4.0 × 10 −11 cm −1 Hz −1/2. Subsequently, the measurement time has been reduced to under 10 min. This standard of performance would enable a variety of high concentration (3-10 %) isotopic measurements, such as medical human breath analysis or animal breath experiments. The extension of this ring-down to the 2 µm region would enable isotopic analysis at ambient concentrations, which, combined with the small size, robust design, and potential for frequent measurements at a remote site, make CRDS technology attractive for remote atmospheric measurement applications.
Methane source pinpointing and attribution is ever more important because of the vast network of ... more Methane source pinpointing and attribution is ever more important because of the vast network of natural gas distribution which has led to a very large emission sources. Ethane can be used as a tracer to distinguish gas sources between biogenic and natural gas. Having this measurement sensitive enough can even distinguish between gas distributors, or maturity through gas wetness. Here we present data obtained using a portable cavity ring-down spectrometer weighing less than 11 kg and consuming less than 35W that simultaneously measures methane and ethane with a raw 1-σ precision of 50ppb and 4.5ppb, respectively at 2 Hz. These precisions allow for a C 2 :C 1 ratio 1-σ measurement of <0.1% above 10ppm in a single measurement. Utilizing a second onboard laser allows for a high precision methane only mode used for surveying and pinpointing. This mode measures at a rate faster than 4Hz with a 1-σ precision of <3ppb. Because methane seepages are highly variable due to air turbulence and mixing right above the ground, correlations in the variations in C 2 H 6 and CH 4 are used to derive a source C 2 :C 1. Additional hardware is needed for steady state concentration measurements to reliably measure the C 2 :C 1 ratio instantaneously. Source discrimination data of local leaks and methane sources using this analysis method are presented. Additionally, two-dimensional plume snapshots are constructed using an integrated onboard GPS to visualize horizontal plane gas propagation.
Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant ... more Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant source distributions. These features create a scale separation between local sources and urban scale emissions estimates known as the Grey-Zone. Modern computational fluid dynamics (CFD) techniques provide a quasi-deterministic, physically based toolset to bridge the scale separation gap between source level dynamics, local measurements, and urban scale emissions inventories. CFD has the capability to represent complex building topography and capture detailed 3D turbulence fields in the urban boundary layer.
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